KSH(1) KSH(1)NAME
ksh, rksh, pfksh - KornShell, a standard/restricted command and programming language
SYNOPSISksh [ ?abcefhiknoprstuvxBCDP ] [ -R file ] [ ?o option ] ... [ - ] [ arg ... ]
DESCRIPTIONKsh is a command and programming language that executes commands read from a terminal or a file. Rksh is a
restricted version of the command interpreter ksh; it is used to set up login names and execution environments
whose capabilities are more controlled than those of the standard shell. Rpfksh is a profile shell version of
the command interpreter ksh; it is used to to execute commands with the attributes specified by the user's pro-
files (see pfexec(1)). See Invocation below for the meaning of arguments to the shell.
Definitions.
A metacharacter is one of the following characters:
;&()|<>new-linespacetab
A blank is a tab or a space. An identifier is a sequence of letters, digits, or underscores starting with a
letter or underscore. Identifiers are used as components of variable names. A vname is a sequence of one or
more identifiers separated by a . and optionally preceded by a .. Vnames are used as function and variable
names. A word is a sequence of characters from the character set defined by the current locale, excluding non-
quoted metacharacters.
A command is a sequence of characters in the syntax of the shell language. The shell reads each command and
carries out the desired action either directly or by invoking separate utilities. A built-in command is a com-
mand that is carried out by the shell itself without creating a separate process. Some commands are built-in
purely for convenience and are not documented here. Built-ins that cause side effects in the shell environment
and built-ins that are found before performing a path search (see Execution below) are documented here. For
historical reasons, some of these built-ins behave differently than other built-ins and are called specialbuilt-ins.
Commands.
A simple-command is a list of variable assignments (see VariableAssignments below) or a sequence of blank sep-
arated words which may be preceded by a list of variable assignments (see Environment below). The first word
specifies the name of the command to be executed. Except as specified below, the remaining words are passed as
arguments to the invoked command. The command name is passed as argument 0 (see exec(2)). The value of a sim-
ple-command is its exit status; 0-255 if it terminates normally; 256+signum if it terminates abnormally (the
name of the signal corresponding to the exit status can be obtained via the -l option of the kill built-in
utility).
A pipeline is a sequence of one or more commands separated by |. The standard output of each command but the
last is connected by a pipe(2) to the standard input of the next command. Each command, except possibly the
last, is run as a separate process; the shell waits for the last command to terminate. The exit status of a
pipeline is the exit status of the last command unless the pipefail option is enabled. Each pipeline can be
preceded by the reservedword! which causes the exit status of the pipeline to become 0 if the exit status of
the last command is non-zero, and 1 if the exit status of the last command is 0.
A list is a sequence of one or more pipelines separated by ;, &, |&, &&, or ||, and optionally terminated by ;,
&, or |&. Of these five symbols, ;, &, and |& have equal precedence, which is lower than that of && and ||.
The symbols && and || also have equal precedence. A semicolon (;) causes sequential execution of the preceding
pipeline; an ampersand (&) causes asynchronous execution of the preceding pipeline (i.e., the shell does not
wait for that pipeline to finish). The symbol |& causes asynchronous execution of the preceding pipeline with
a two-way pipe established to the parent shell; the standard input and output of the spawned pipeline can be
written to and read from by the parent shell by applying the redirection operators <& and >& with arg p to com-
mands and by using -p option of the built-in commands read and print described later. The symbol && (||)
causes the list following it to be executed only if the preceding pipeline returns a zero (non-zero) value.
One or more new-lines may appear in a list instead of a semicolon, to delimit a command. The first item of
the first pipeline of a list that is a simple command not beginning with a redirection, and not occurring
within a while, until, or iflist, can be preceded by a semicolon. This semicolon is ignored unless the showme
option is enabled as described with the set built-in below.
A command is either a simple-command or one of the following. Unless otherwise stated, the value returned by a
command is that of the last simple-command executed in the command.
forvname [ inword ... ] ;dolist;done
Each time a for command is executed, vname is set to the next word taken from the inword list. If inword ... is omitted, then the for command executes the dolist once for each positional parameter that
is set starting from 1 (see ParameterExpansion below). Execution ends when there are no more words in
the list.
for(( [expr1] ; [expr2] ; [expr3] ));dolist;done
The arithmetic expression expr1 is evaluated first (see Arithmeticevaluation below). The arithmetic
expression expr2 is repeatedly evaluated until it evaluates to zero and when non-zero, list is executed
and the arithmetic expression expr3 evaluated. If any expression is omitted, then it behaves as if it
evaluated to 1.
selectvname [ inword ... ] ;dolist;done
A select command prints on standard error (file descriptor 2) the set of words, each preceded by a num-
ber. If inword ... is omitted, then the positional parameters starting from 1 are used instead (see
ParameterExpansion below). The PS3 prompt is printed and a line is read from the standard input. If
this line consists of the number of one of the listed words, then the value of the variable vname is set
to the word corresponding to this number. If this line is empty, the selection list is printed again.
Otherwise the value of the variable vname is set to null. The contents of the line read from standard
input is saved in the variable REPLY. The list is executed for each selection until a break or end-of-file is encountered. If the REPLY variable is set to null by the execution of list, then the selection
list is printed before displaying the PS3 prompt for the next selection.
casewordin [ [(]pattern [ | pattern ] ... )list;; ] ... esac
A case command executes the list associated with the first pattern that matches word. The form of the
patterns is the same as that used for file-name generation (see FileNameGeneration below). The ;;
operator causes execution of case to terminate. If ;& is used in place of ;; the next subsequent list,
if any, is executed.
iflist;thenlist [ ;eliflist;thenlist ] ... [ ;elselist ] ;fi
The list following if is executed and, if it returns a zero exit status, the list following the first
then is executed. Otherwise, the list following elif is executed and, if its value is zero, the list
following the next then is executed. Failing each successive eliflist, the elselist is executed. If
the iflist has non-zero exit status and there is no elselist, then the if command returns a zero exit
status.
whilelist;dolist;doneuntillist;dolist;done
A while command repeatedly executes the whilelist and, if the exit status of the last command in the
list is zero, executes the dolist; otherwise the loop terminates. If no commands in the dolist are
executed, then the while command returns a zero exit status; until may be used in place of while to
negate the loop termination test.
((expression))
The expression is evaluated using the rules for arithmetic evaluation described below. If the value of
the arithmetic expression is non-zero, the exit status is 0, otherwise the exit status is 1.
(list)
Execute list in a separate environment. Note, that if two adjacent open parentheses are needed for
nesting, a space must be inserted to avoid evaluation as an arithmetic command as described above.
{list;}list is simply executed. Note that unlike the metacharacters ( and ), { and } are reservedwords and
must occur at the beginning of a line or after a ; in order to be recognized.
[[expression]]
Evaluates expression and returns a zero exit status when expression is true. See ConditionalExpres-sions below, for a description of expression.
functionvarname{list;}varname(){list;}
Define a function which is referenced by varname. A function whose varname contains a . is called a
discipline function and the portion of the varname preceding the last . must refer to an existing
variable. The body of the function is the list of commands between { and }. A function defined with
the functionvarname syntax can also be used as an argument to the . special built-in command to get
the equivalent behavior as if the varname() syntax were used to define it. (See Functions below.)
namespaceidentifier{list;}
Defines or uses the name space identifier and runs the commands in list in this name space. (See NameSpaces below.)
& [ name [ arg... ] ]
Causes subsequent list commands terminated by & to be placed in the background job pool name. If name
is omitted a default unnamed pool is used. Commands in a named background pool may be executed
remotely.
time [ pipeline ]
If pipeline is omitted the user and system time for the current shell and completed child processes is
printed on standard error. Otherwise, pipeline is executed and the elapsed time as well as the user and
system time are printed on standard error. The TIMEFORMAT variable may be set to a format string that
specifies how the timing information should be displayed. See ShellVariables below for a description
of the TIMEFORMAT variable.
The following reserved words are recognized as reserved only when they are the first word of a command and are
not quoted:
ifthenelseelifficaseesacforwhileuntildodone{}functionselecttime[[]]!VariableAssignments.
One or more variable assignments can start a simple command or can be arguments to the typeset, enum, export,
or readonly special built-in commands as well as to other declaration commands created as types. The syntax
for an assignment is of the form:
varname=wordvarname[word]=word
No space is permitted between varname and the = or between = and word.
varname=(assign_list)
No space is permitted between varname and the =. The variable varname is unset before the assignment.
An assign_list can be one of the following:
word ...
Indexed array assignment.
[word]=word ...
Associative array assignment. If preceded by typeset-a this will create an indexed
array instead.
assignment ...
Compound variable assignment. This creates a compound variable varname with sub-vari-
ables of the form varname.name, where name is the name portion of assignment. The value
of varname will contain all the assignment elements. Additional assignments made to sub-
variables of varname will also be displayed as part of the value of varname. If no
assignments are specified, varname will be a compound variable allowing subsequence child
elements to be defined.
typeset [options] assignment ...
Nested variable assignment. Multiple assignments can be specified by separating each of
them with a ;. The previous value is unset before the assignment. Other declaration
commands such as readonly,enum, and other declaration commands can be used in place of
typeset.
.filename
Include the assignment commands contained in filename.
In addition, a += can be used in place of the = to signify adding to or appending to the previous value. When
+= is applied to an arithmetic type, word is evaluated as an arithmetic expression and added to the current
value. When applied to a string variable, the value defined by word is appended to the value. For compound
assignments, the previous value is not unset and the new values are appended to the current ones provided that
the types are compatible.
The right hand side of a variable assignment undergoes all the expansion listed below except word splitting,
brace expansion, and file name generation. When the left hand side is an assignment is a compound variable and
the right hand is the name of a compound variable, the compound variable on the right will be copied or
appended to the compound variable on the left.
Comments.
A word beginning with # causes that word and all the following characters up to a new-line to be ignored.
Aliasing.
The first word of each command is replaced by the text of an alias if an alias for this word has been defined.
An alias name consists of any number of characters excluding metacharacters, quoting characters, file expansion
characters, parameter expansion and command substitution characters, the characters / and =. The replacement
string can contain any valid shell script including the metacharacters listed above. The first word of each
command in the replaced text, other than any that are in the process of being replaced, will be tested for
aliases. If the last character of the alias value is a blank then the word following the alias will also be
checked for alias substitution. Aliases can be used to redefine built-in commands but cannot be used to rede-
fine the reserved words listed above. Aliases can be created and listed with the alias command and can be
removed with the unalias command.
Aliasing is performed when scripts are read, not while they are executed. Therefore, for an alias to take
effect, the alias definition command has to be executed before the command which references the alias is read.
The following aliases are compiled into the shell but can be unset or redefined:
autoload=?typeset-fu?command=?command?compound=?typeset-C?fc=histfloat=?typeset-lE?functions=?typeset-f?hash=?alias-t--?history=?hist-l?integer=?typeset-li?nameref=?typeset-n?nohup=?nohup?r=?hist-s?redirect=?commandexec?source=?command.?stop=?kill-sSTOP?suspend=?kill-sSTOP$$?times=?{{time;}2>&1;}?type=?whence-v?TildeSubstitution.
After alias substitution is performed, each word is checked to see if it begins with an unquoted ~. For tilde
substitution, word also refers to the word portion of parameter expansion (see ParameterExpansion below). If
it does, then the word up to a / is checked to see if it matches a user name in the password database (See get-pwname(3).) If a match is found, the ~ and the matched login name are replaced by the login directory of the
matched user. If no match is found, the original text is left unchanged. A ~ by itself, or in front of a /,
is replaced by $HOME. A ~ followed by a + or - is replaced by the value of $PWD and $OLDPWD respectively.
In addition, when expanding a variableassignment, tilde substitution is attempted when the value of the
assignment begins with a ~, and when a ~ appears after a :. The : also terminates a ~ login name.
CommandSubstitution.
The standard output from a command list enclosed in parentheses preceded by a dollar sign ( $(list) ), or in a
brace group preceded by a dollar sign ( ${list;} ), or in a pair of grave accents (``) may be used as part or
all of a word; trailing new-lines are removed. In the second case, the { and } are treated as a reserved words
so that { must be followed by a blank and } must appear at the beginning of the line or follow a ;. In the
third (obsolete) form, the string between the quotes is processed for special quoting characters before the
command is executed (see Quoting below). The command substitution $(catfile) can be replaced by the equiva-
lent but faster $(<file). The command substitution $(n<#) will expand to the current byte offset for file
descriptor n. Except for the second form, the command list is run in a subshell so that no side effects are
possible. For the second form, the final } will be recognized as a reserved word after any token.
ArithmeticSubstitution.
An arithmetic expression enclosed in double parentheses preceded by a dollar sign ( $(()) ) is replaced by the
value of the arithmetic expression within the double parentheses.
ProcessSubstitution.
Each command argument of the form <(list) or >(list) will run process list asynchronously connected to some
file in /dev/fd if this directory exists, or else a fifo a temporary directory. The name of this file will
become the argument to the command. If the form with > is selected then writing on this file will provide
input for list. If < is used, then the file passed as an argument will contain the output of the list process.
For example,
paste<(cut-f1file1)<(cut-f3file2)|tee>(process1)>(process2)cuts fields 1 and 3 from the files file1 and file2 respectively, pastes the results together, and sends it to
the processes process1 and process2, as well as putting it onto the standard output. Note that the file, which
is passed as an argument to the command, is a UNIX pipe(2) so programs that expect to lseek(2) on the file will
not work.
Process substitution of the form <(list) can also be used with the < redirection operator which causes the out-
put of list to be standard input or the input for whatever file descriptor is specified.
ParameterExpansion.
A parameter is a variable, one or more digits, or any of the characters *, @, #, ?, -, $, and !. A variable is
denoted by a vname. To create a variable whose vname contains a ., a variable whose vname consists of every-
thing before the last . must already exist. A variable has a value and zero or more attributes. Variables can
be assigned values and attributes by using the typeset special built-in command. The attributes supported by
the shell are described later with the typeset special built-in command. Exported variables pass values and
attributes to the environment.
The shell supports both indexed and associative arrays. An element of an array variable is referenced by a
subscript. A subscript for an indexed array is denoted by an arithmeticexpression (see Arithmeticevaluation
below) between a [ and a ]. To assign values to an indexed array, use vname=(value ...) or set-Avnamevalue
... . The value of all non-negative subscripts must be in the range of 0 through 4,194,303. A negative sub-
script is treated as an offset from the maximum current index +1 so that -1 refers to the last element.
Indexed arrays can be declared with the -a option to typeset. Indexed arrays need not be declared. Any refer-
ence to a variable with a valid subscript is legal and an array will be created if necessary.
An associative array is created with the -A option to typeset. A subscript for an associative array is denoted
by a string enclosed between [ and ].
Referencing any array without a subscript is equivalent to referencing the array with subscript 0.
The value of a variable may be assigned by writing:
vname=value [ vname=value ] ...
or
vname[subscript]=value [ vname[subscript]=value ] ...
Note that no space is allowed before or after the =.
Attributes assigned by the typeset special built-in command apply to all elements of the array. An array ele-
ment can be a simple variable, a compound variable or an array variable. An element of an indexed array can be
either an indexed array or an associative array. An element of an associative array can also be either. To
refer to an array element that is part of an array element, concatenate the subscript in brackets. For exam-
ple, to refer to the foobar element of an associative array that is defined as the third element of the indexed
array, use ${vname[3][foobar]}
A nameref is a variable that is a reference to another variable. A nameref is created with the -n attribute of
typeset. The value of the variable at the time of the typeset command becomes the variable that will be refer-
enced whenever the nameref variable is used. The name of a nameref cannot contain a .. When a variable or
function name contains a ., and the portion of the name up to the first . matches the name of a nameref, the
variable referred to is obtained by replacing the nameref portion with the name of the variable referenced by
the nameref. If a nameref is used as the index of a for loop, a name reference is established for each item in
the list. A nameref provides a convenient way to refer to the variable inside a function whose name is passed
as an argument to a function. For example, if the name of a variable is passed as the first argument to a
function, the command
typeset-nvar=$1
inside the function causes references and assignments to var to be references and assignments to the variable
whose name has been passed to the function.
If any of the floating point attributes, -E, -F, or -X, or the integer attribute, -i, is set for vname, then
the value is subject to arithmetic evaluation as described below.
Positional parameters, parameters denoted by a number, may be assigned values with the set special built-in
command. Parameter $0 is set from argument zero when the shell is invoked.
The character $ is used to introduce substitutable parameters.
${parameter}
The shell reads all the characters from ${ to the matching } as part of the same word even if it con-
tains braces or metacharacters. The value, if any, of the parameter is substituted. The braces are
required when parameter is followed by a letter, digit, or underscore that is not to be interpreted as
part of its name, when the variable name contains a .. The braces are also required when a variable is
subscripted unless it is part of an Arithmetic Expression or a Conditional Expression. If parameter is
one or more digits then it is a positional parameter. A positional parameter of more than one digit
must be enclosed in braces. If parameter is * or @, then all the positional parameters, starting with
$1, are substituted (separated by a field separator character). If an array vname with last subscript *@, or for index arrays of the form sub1..sub2. is used, then the value for each of the elements
between sub1 and sub2 inclusive (or all elements for * and @) is substituted, separated by the first
character of the value of IFS.
${#parameter}
If parameter is * or @, the number of positional parameters is substituted. Otherwise, the length of
the value of the parameter is substituted.
${#vname[*]}${#vname[@]}
The number of elements in the array vname is substituted.
${@vname}
Expands to the type name (See TypeVariables below) or attributes of the variable referred to by vname.
${!vname}
Expands to the name of the variable referred to by vname. This will be vname except when vname is a
name reference.
${!vname[subscript]}
Expands to name of the subscript unless subscript is *, @. or of the form sub1..sub2. When sub-script is *, the list of array subscripts for vname is generated. For a variable that is not an array,
the value is 0 if the variable is set. Otherwise it is null. When subscript is @, same as above,
except that when used in double quotes, each array subscript yields a separate argument. When subscript
is of the form sub1..sub2 it expands to the list of subscripts between sub1 and sub2 inclusive using
the same quoting rules as @.
${!prefix*}
Expands to the names of the variables whose names begin with prefix.
${parameter:-word}
If parameter is set and is non-null then substitute its value; otherwise substitute word.
${parameter:=word}
If parameter is not set or is null then set it to word; the value of the parameter is then substituted.
Positional parameters may not be assigned to in this way.
${parameter:?word}
If parameter is set and is non-null then substitute its value; otherwise, print word and exit from the
shell (if not interactive). If word is omitted then a standard message is printed.
${parameter:+word}
If parameter is set and is non-null then substitute word; otherwise substitute nothing.
In the above, word is not evaluated unless it is to be used as the substituted string, so that, in the follow-
ing example, pwd is executed only if d is not set or is null:
print ${d:-$(pwd)}
If the colon ( :) is omitted from the above expressions, then the shell only checks whether parameter is set
or not.
${parameter:offset:length}${parameter:offset}
Expands to the portion of the value of parameter starting at the character (counting from 0) determined
by expanding offset as an arithmetic expression and consisting of the number of characters determined by
the arithmetic expression defined by length. In the second form, the remainder of the value is used.
If A negative offset counts backwards from the end of parameter. Note that one or more blanks is
required in front of a minus sign to prevent the shell from interpreting the operator as :-. If parame-ter is * or @, or is an array name indexed by * or @, then offset and length refer to the array index
and number of elements respectively. A negative offset is taken relative to one greater than the high-
est subscript for indexed arrays. The order for associate arrays is unspecified.
${parameter#pattern}${parameter##pattern}
If the shell pattern matches the beginning of the value of parameter, then the value of this expansion
is the value of the parameter with the matched portion deleted; otherwise the value of this parameter is
substituted. In the first form the smallest matching pattern is deleted and in the second form the
largest matching pattern is deleted. When parameter is @, *, or an array variable with subscript @ or
*, the substring operation is applied to each element in turn.
${parameter%pattern}${parameter%%pattern}
If the shell pattern matches the end of the value of parameter, then the value of this expansion is the
value of the parameter with the matched part deleted; otherwise substitute the value of parameter. In
the first form the smallest matching pattern is deleted and in the second form the largest matching pat-
tern is deleted. When parameter is @, *, or an array variable with subscript @ or *, the substring
operation is applied to each element in turn.
${parameter/pattern/string}${parameter//pattern/string}${parameter/#pattern/string}${parameter/%pattern/string}
Expands parameter and replaces the longest match of pattern with the given string. Each occurrence of
\n in string is replaced by the portion of parameter that matches the n-th sub-pattern. In the first
form, only the first occurrence of pattern is replaced. In the second form, each match for pattern is
replaced by the given string. The third form restricts the pattern match to the beginning of the string
while the fourth form restricts the pattern match to the end of the string. When string is null, the
pattern will be deleted and the / in front of string may be omitted. When parameter is @, *, or an
array variable with subscript @ or *, the substitution operation is applied to each element in turn. In
this case, the string portion of word will be re-evaluated for each element.
The following parameters are automatically set by the shell:
# The number of positional parameters in decimal.
- Options supplied to the shell on invocation or by the set command.
? The decimal value returned by the last executed command.
$ The process number of this shell.
_ Initially, the value of _ is an absolute pathname of the shell or script being executed as passed
in the environment. Subsequently it is assigned the last argument of the previous command. This
parameter is not set for commands which are asynchronous. This parameter is also used to hold
the name of the matching MAIL file when checking for mail. While defining a compound variable or
a type, _ is initialized as a reference to the compound variable or type. When a discipline
function is invoked, _ is initialized as a reference to the variable associated with the call to
this function. Finally when _ is used as the name of the first variable of a type definition,
the new type is derived from the type of the first variable (See TypeVariables below.).
! The process id or the pool name and job number of the last background command invoked or the most
recent job put in the background with the bg built-in command. Background jobs started in a
named pool will be in the form pool.number where pool is the pool name and number is the job num-
ber within that pool.
.sh.command
When processing a DEBUG trap, this variable contains the current command line that is about to
run.
.sh.edchar
This variable contains the value of the keyboard character (or sequence of characters if the
first character is an ESC, ascii 033) that has been entered when processing a KEYBD trap (see KeyBindings below). If the value is changed as part of the trap action, then the new value replaces
the key (or key sequence) that caused the trap.
.sh.edcol
The character position of the cursor at the time of the most recent KEYBD trap.
.sh.edmode
The value is set to ESC when processing a KEYBD trap while in vi insert mode. (See ViEditingMode below.) Otherwise, .sh.edmode is null when processing a KEYBD trap.
.sh.edtext
The characters in the input buffer at the time of the most recent KEYBD trap. The value is null
when not processing a KEYBD trap.
.sh.file
The pathname of the file than contains the current command.
.sh.fun
The name of the current function that is being executed.
.sh.level
Set to the current function depth. This can be changed inside a DEBUG trap and will set the con-
text to the specified level.
.sh.lineno
Set during a DEBUG trap to the line number for the caller of each function.
.sh.match
An indexed array which stores the most recent match and sub-pattern matches after conditional
pattern matches that match and after variables expansions using the operators #, %, or /. The
0-th element stores the complete match and the i-th. element stores the i-th submatch. The
.sh.match variable becomes unset when the variable that has expanded is assigned a new value.
.sh.math
Used for defining arithmetic functions (see Arithmeticevaluation below). and stores the list of
user defined arithmetic functions.
.sh.name
Set to the name of the variable at the time that a discipline function is invoked.
.sh.subscript
Set to the name subscript of the variable at the time that a discipline function is invoked.
.sh.subshell
The current depth for subshells and command substitution.
.sh.value
Set to the value of the variable at the time that the set or append discipline function is
invoked. When a user defined arithmetic function is invoked, the value of .sh.value is saved and
.sh.value is set to long double precision floating point. .sh.value is restored when the func-
tion returns.
.sh.version
Set to a value that identifies the version of this shell.
KSH_VERSION
A name reference to .sh.version.
LINENO The current line number within the script or function being executed.
OLDPWD The previous working directory set by the cd command.
OPTARG The value of the last option argument processed by the getopts built-in command.
OPTIND The index of the last option argument processed by the getopts built-in command.
PPID The process number of the parent of the shell.
PWD The present working directory set by the cd command.
RANDOM Each time this variable is referenced, a random integer, uniformly distributed between 0 and
32767, is generated. The sequence of random numbers can be initialized by assigning a numeric
value to RANDOM.
REPLY This variable is set by the select statement and by the read built-in command when no arguments
are supplied.
SECONDS
Each time this variable is referenced, the number of seconds since shell invocation is returned.
If this variable is assigned a value, then the value returned upon reference will be the value
that was assigned plus the number of seconds since the assignment.
SHLVL An integer variable the is incremented each time the shell is invoked and is exported. If SHLVL
is not in the environment when the shell is invoked, it is set to 1.
The following variables are used by the shell:
CDPATH The search path for the cd command.
COLUMNS
If this variable is set, the value is used to define the width of the edit window for the shell
edit modes and for printing select lists.
EDITOR If the VISUAL variable is not set, the value of this variable will be checked for the patterns as
described with VISUAL below and the corresponding editing option (see Special Command set below)
will be turned on.
ENV If this variable is set, then parameter expansion, command substitution, and arithmetic substitu-
tion are performed on the value to generate the pathname of the script that will be executed when
the shell is invoked interactively (see Invocation below). This file is typically used for alias
and function definitions. The default value is $HOME/.kshrc. On systems that support a system
wide /etc/ksh.kshrc initialization file, if the filename generated by the expansion of ENV
begins with /./ or ././ the system wide initialization file will not be executed.
FCEDIT Obsolete name for the default editor name for the hist command. FCEDIT is not used when HISTEDIT
is set.
FIGNORE
A pattern that defines the set of filenames that will be ignored when performing filename match-
ing.
FPATH The search path for function definitions. The directories in this path are searched for a file
with the same name as the function or command when a function with the -u attribute is referenced
and when a command is not found. If an executable file with the name of that command is found,
then it is read and executed in the current environment. Unlike PATH, the current directory must
be represented explicitly by . rather than by adjacent : characters or a beginning or ending :.
HISTCMD
Number of the current command in the history file.
HISTEDIT
Name for the default editor name for the hist command.
HISTFILE
If this variable is set when the shell is invoked, then the value is the pathname of the file
that will be used to store the command history (see CommandRe-entry below).
HISTSIZE
If this variable is set when the shell is invoked, then the number of previously entered commands
that are accessible by this shell will be greater than or equal to this number. The default is
512.
HOME The default argument (home directory) for the cd command.
IFS Internal field separators, normally space, tab, and new-line that are used to separate the
results of command substitution or parameter expansion and to separate fields with the built-in
command read. The first character of the IFS variable is used to separate arguments for the "$*"
substitution (see Quoting below). Each single occurrence of an IFS character in the string to be
split, that is not in the isspace character class, and any adjacent characters in IFS that are in
the isspace character class, delimit a field. One or more characters in IFS that belong to the
isspace character class, delimit a field. In addition, if the same isspace character appears
consecutively inside IFS, this character is treated as if it were not in the isspace class, so
that if IFS consists of two tab characters, then two adjacent tab characters delimit a null
field.
JOBMAX This variable defines the maximum number running background jobs that can run at a time. When
this limit is reached, the shell will wait for a job to complete before staring a new job.
LANG This variable determines the locale category for any category not specifically selected with a
variable starting with LC_ or LANG.
LC_ALL This variable overrides the value of the LANG variable and any other LC_ variable.
LC_COLLATE
This variable determines the locale category for character collation information.
LC_CTYPE
This variable determines the locale category for character handling functions. It determines the
character classes for pattern matching (see FileNameGeneration below).
LC_NUMERIC
This variable determines the locale category for the decimal point character.
LINES If this variable is set, the value is used to determine the column length for printing select
lists. Select lists will print vertically until about two-thirds of LINES lines are filled.
MAIL If this variable is set to the name of a mail file and the MAILPATH variable is not set, then the
shell informs the user of arrival of mail in the specified file.
MAILCHECK
This variable specifies how often (in seconds) the shell will check for changes in the modifica-
tion time of any of the files specified by the MAILPATH or MAIL variables. The default value is
600 seconds. When the time has elapsed the shell will check before issuing the next prompt.
MAILPATH
A colon ( : ) separated list of file names. If this variable is set, then the shell informs the
user of any modifications to the specified files that have occurred within the last MAILCHECK
seconds. Each file name can be followed by a ? and a message that will be printed. The message
will undergo parameter expansion, command substitution, and arithmetic substitution with the
variable $_ defined as the name of the file that has changed. The default message is youhavemailin$_.PATH The search path for commands (see Execution below). The user may not change PATH if executing
under rksh (except in .profile).PS1 The value of this variable is expanded for parameter expansion, command substitution, and arith-
metic substitution to define the primary prompt string which by default is ''$''. The character
! in the primary prompt string is replaced by the command number (see CommandRe-entry below).
Two successive occurrences of ! will produce a single ! when the prompt string is printed.
PS2 Secondary prompt string, by default ''> ''.
PS3 Selection prompt string used within a select loop, by default ''#? ''.
PS4 The value of this variable is expanded for parameter evaluation, command substitution, and arith-
metic substitution and precedes each line of an execution trace. By default, PS4 is ''+ ''. In
addition when PS4 is unset, the execution trace prompt is also ''+ ''.
SHELL The pathname of the shell is kept in the environment. At invocation, if the basename of this
variable is rsh, rksh, or krsh, then the shell becomes restricted. If it is pfsh or pfksh, then
the shell becomes a profile shell (see pfexec(1)).
TIMEFORMAT
The value of this parameter is used as a format string specifying how the timing information for
pipelines prefixed with the time reserved word should be displayed. The % character introduces a
format sequence that is expanded to a time value or other information. The format sequences and
their meanings are as follows.
%% A literal %.
%[p][l]R The elapsed time in seconds.
%[p][l]U The number of CPU seconds spent in user mode.
%[p][l]S The number of CPU seconds spent in system mode.
%P The CPU percentage, computed as (U + S) / R.
The brackets denote optional portions. The optional p is a digit specifying the precision, the
number of fractional digits after a decimal point. A value of 0 causes no decimal point or frac-
tion to be output. At most three places after the decimal point can be displayed; values of p
greater than 3 are treated as 3. If p is not specified, the value 3 is used.
The optional l specifies a longer format, including hours if greater than zero, minutes, and sec-
onds of the form HHhMMmSS.FFs. The value of p determines whether or not the fraction is
included.
All other characters are output without change and a trailing newline is added. If unset, the
default value, $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS', is used. If the value is null, no timing
information is displayed.
TMOUT If set to a value greater than zero, TMOUT will be the default timeout value for the read built-
in command. The select compound command terminates after TMOUT seconds when input is from a ter-
minal. Otherwise, the shell will terminate if a line is not entered within the prescribed number
of seconds while reading from a terminal. (Note that the shell can be compiled with a maximum
bound for this value which cannot be exceeded.)
VISUAL If the value of this variable matches the pattern *[Vv][Ii]*, then the vi option (see Special
Command set below) is turned on. If the value matches the pattern *gmacs*, the gmacs option is
turned on. If the value matches the pattern *macs*, then the emacs option will be turned on.
The value of VISUAL overrides the value of EDITOR.
The shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK, FCEDIT, TMOUT and IFS, while HOME,
SHELL, ENV, and MAIL are not set at all by the shell (although HOMEis set by login(1)). On some systems MAIL
and SHELL are also set by login(1).
FieldSplitting.
After parameter expansion and command substitution, the results of substitutions are scanned for the field sep-
arator characters (those found in IFS) and split into distinct fields where such characters are found.
Explicit null fields ("" or ??) are retained. Implicit null fields (those resulting from parameters that have
no values or command substitutions with no output) are removed.
If the braceexpand (-B) option is set then each of the fields resulting from IFS are checked to see if they
contain one or more of the brace patterns {*,*}, {l1..l2} , {n1..n2} , {n1..n2%fmt} , {n1..n2..n3} , or
{n1..n2..n3%fmt} , where * represents any character, l1,l2 are letters and n1,n2,n3 are signed numbers and fmt
is a format specified as used by printf. In each case, fields are created by prepending the characters before
the { and appending the characters after the } to each of the strings generated by the characters between the {
and }. The resulting fields are checked to see if they have any brace patterns.
In the first form, a field is created for each string between { and ,, between , and ,, and between , and }.
The string represented by * can contain embedded matching { and } without quoting. Otherwise, each { and }
with * must be quoted.
In the seconds form, l1 and l2 must both be either upper case or both be lower case characters in the C locale.
In this case a field is created for each character from l1 thru l2.
In the remaining forms, a field is created for each number starting at n1 and continuing until it reaches n2
incrementing n1 by n3. The cases where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1 otherwise.
If forms which specify %fmt any format flags, widths and precisions can be specified and fmt can end in any of
the specifiers cdiouxX. For example, {a,z}{1..5..3%02d}{b..c}x expands to the 8 fields, a01bx, a01cx, a04bx,
a04cx, z01bx, z01cx, z04bx and z4cx.
FileNameGeneration.
Following splitting, each field is scanned for the characters *, ?, (, and [ unless the -f option has been set.
If one of these characters appears, then the word is regarded as a pattern. Each file name component that con-
tains any pattern character is replaced with a lexicographically sorted set of names that matches the pattern
from that directory. If no file name is found that matches the pattern, then that component of the filename is
left unchanged unless the pattern is prefixed with ~(N) in which case it is removed as described below. If
FIGNORE is set, then each file name component that matches the pattern defined by the value of FIGNORE is
ignored when generating the matching filenames. The names . and .. are also ignored. If FIGNORE is not set,
the character . at the start of each file name component will be ignored unless the first character of the
pattern corresponding to this component is the character . itself. Note, that for other uses of pattern
matching the / and . are not treated specially.
* Matches any string, including the null string. When used for filename expansion, if the globstar
option is on, two adjacent *'s by itself will match all files and zero or more directories and
subdirectories. If followed by a / then only directories and subdirectories will match.
? Matches any single character.
[...] Matches any one of the enclosed characters. A pair of characters separated by - matches any
character lexically between the pair, inclusive. If the first character following the opening [
is a ! or ^ then any character not enclosed is matched. A - can be included in the character
set by putting it as the first or last character.
Within [ and ], character classes can be specified with the syntax [:class:] where class is one
of the following classes defined in the ANSI-C standard: (Note that word is equivalent to alnum
plus the character _.)
alnumalphablankcntrldigitgraphlowerprintpunctspaceupperwordxdigit
Within [ and ], an equivalence class can be specified with the syntax [=c=] which matches all
characters with the same primary collation weight (as defined by the current locale) as the char-
acter c. Within [ and ], [.symbol.] matches the collating symbol symbol.
A pattern-list is a list of one or more patterns separated from each other with a & or |. A & signifies that
all patterns must be matched whereas | requires that only one pattern be matched. Composite patterns can be
formed with one or more of the following sub-patterns:
?(pattern-list)
Optionally matches any one of the given patterns.
*(pattern-list)
Matches zero or more occurrences of the given patterns.
+(pattern-list)
Matches one or more occurrences of the given patterns.
{n}(pattern-list)
Matches n occurrences of the given patterns.
{m,n}(pattern-list)
Matches from m to n occurrences of the given patterns. If m is omitted, 0 will be used. If n is
omitted at least m occurrences will be matched.
@(pattern-list)
Matches exactly one of the given patterns.
!(pattern-list)
Matches anything except one of the given patterns.
By default, each pattern, or sub-pattern will match the longest string possible consistent with generating the
longest overall match. If more than one match is possible, the one starting closest to the beginning of the
string will be chosen. However, for each of the above compound patterns a - can be inserted in front of the (
to cause the shortest match to the specified pattern-list to be used.
When pattern-list is contained within parentheses, the backslash character \ is treated specially even when
inside a character class. All ANSI-C character escapes are recognized and match the specified character. In
addition the following escape sequences are recognized:
\d Matches any character in the digit class.
\D Matches any character not in the digit class.
\s Matches any character in the space class.
\S Matches any character not in the space class.
\w Matches any character in the word class.
\W Matches any character not in the word class.
A pattern of the form %(pattern-pair(s)) is a sub-pattern that can be used to match nested character expres-
sions. Each pattern-pair is a two character sequence which cannot contain & or |. The first pattern-pair
specifies the starting and ending characters for the match. Each subsequent pattern-pair represents the begin-
ning and ending characters of a nested group that will be skipped over when counting starting and ending char-
acter matches. The behavior is unspecified when the first character of a pattern-pair is alpha-numeric except
for the following:
D Causes the ending character to terminate the search for this pattern without finding a match.
E Causes the ending character to be interpreted as an escape character.
L Causes the ending character to be interpreted as a quote character causing all characters to be
ignored when looking for a match.
Q Causes the ending character to be interpreted as a quote character causing all characters other
than any escape character to be ignored when looking for a match.
Thus, %({}Q"E\), matches characters starting at { until the matching } is found not counting any { or } that is
inside a double quoted string or preceded by the escape character \. Without the {} this pattern matches any C
language string.
Each sub-pattern in a composite pattern is numbered, starting at 1, by the location of the ( within the pat-
tern. The sequence \n, where n is a single digit and \n comes after the n-th. sub-pattern, matches the same
string as the sub-pattern itself.
Finally a pattern can contain sub-patterns of the form ~(options:pattern-list), where either options or :pat-tern-list can be omitted. Unlike the other compound patterns, these sub-patterns are not counted in the num-
bered sub-patterns. :pattern-list must be omitted for options F, G, N, and V below. If options is present,
it can consist of one or more of the following:
+ Enable the following options. This is the default.
- Disable the following options.
E The remainder of the pattern uses extended regular expression syntax like the egrep(1) command.
F The remainder of the pattern uses fgrep(1) expression syntax.
G The remainder of the pattern uses basic regular expression syntax like the grep(1) command.
K The remainder of the pattern uses shell pattern syntax. This is the default.
N This is ignored. However, when it is the first letter and is used with file name generation, and
no matches occur, the file pattern expands to the empty string.
X The remainder of the pattern uses augmented regular expression syntax like the xgrep(1) command.
P The remainder of the pattern uses perl(1) regular expression syntax. Not all perl regular
expression syntax is currently implemented.
V The remainder of the pattern uses System V regular expression syntax.
i Treat the match as case insensitive.
g File the longest match (greedy). This is the default.
l Left anchor the pattern. This is the default for K style patterns.
r Right anchor the pattern. This is the default for K style patterns.
If both options and :pattern-list are specified, then the options apply only to pattern-list. Otherwise,
these options remain in effect until they are disabled by a subsequent ~(...) or at the end of the sub-pattern
containing ~(...).
Quoting.
Each of the metacharacters listed earlier (see Definitions above) has a special meaning to the shell and causes
termination of a word unless quoted. A character may be quoted (i.e., made to stand for itself) by preceding
it with a \. The pair \new-line is removed. All characters enclosed between a pair of single quote marks (??)
that is not preceded by a $ are quoted. A single quote cannot appear within the single quotes. A single
quoted string preceded by an unquoted $ is processed as an ANSI-C string except for the following:
\0 Causes the remainder of the string to be ignored.
\E Equivalent to the escape character (ascii 033),
\e Equivalent to the escape character (ascii 033),
\cx Expands to the character control-x.
\C[.name.]
Expands to the collating element name.
Inside double quote marks (""), parameter and command substitution occur and \ quotes the characters \, `, ",
and $. A $ in front of a double quoted string will be ignored in the "C" or "POSIX" locale, and may cause the
string to be replaced by a locale specific string otherwise. The meaning of $* and $@ is identical when not
quoted or when used as a variable assignment value or as a file name. However, when used as a command argu-
ment, "$*" is equivalent to "$1d$2d...", where d is the first character of the IFS variable, whereas "$@" is
equivalent to "$1""$2" .... Inside grave quote marks (``), \ quotes the characters \, `, and $. If the grave
quotes occur within double quotes, then \ also quotes the character ".
The special meaning of reserved words or aliases can be removed by quoting any character of the reserved word.
The recognition of function names or built-in command names listed below cannot be altered by quoting them.
ArithmeticEvaluation.
The shell performs arithmetic evaluation for arithmetic substitution, to evaluate an arithmetic command, to
evaluate an indexed array subscript, and to evaluate arguments to the built-in commands shift and let. Evalua-
tions are performed using double precision floating point arithmetic or long double precision floating point
for systems that provide this data type. Floating point constants follow the ANSI-C programming language
floating point conventions. The floating point constants Nan and Inf can be use to represent "not a number"
and infinity respectively. Integer constants follow the ANSI-C programming language integer constant conven-
tions although only single byte character constants are recognized and character casts are not recognized. In
addition constants can be of the form [base#]n where base is a decimal number between two and sixty-four repre-
senting the arithmetic base and n is a number in that base. The digits above 9 are represented by the lower
case letters, the upper case letters, @, and _ respectively. For bases less than or equal to 36, upper and
lower case characters can be used interchangeably.
An arithmetic expression uses the same syntax, precedence, and associativity of expression as the C language.
All the C language operators that apply to floating point quantities can be used. In addition, the operator **
can be used for exponentiation. It has higher precedence than multiplication and is left associative. In
addition, when the value of an arithmetic variable or sub-expression can be represented as a long integer, all
C language integer arithmetic operations can be performed. Variables can be referenced by name within an
arithmetic expression without using the parameter expansion syntax. When a variable is referenced, its value
is evaluated as an arithmetic expression.
Any of the following math library functions that are in the C math library can be used within an arithmetic
expression:
absacosacoshasinasinhatanatan2atanhcbrtceilcopysigncoscosherferfcexpexp2expm1fabsfpclassifyfdimfinitefloorfmafmaxfminfmodhypotilogbintisfinitesinfisnanisnormalissubnormalissuborderediszeroj0j1jnlgammaloglog10log2logbnearbyintnextafternexttowardpowremainderrintroundscanbsign-bitsinsinhsqrttantanhtgammatruncy0y1yn In addition, arithmetic functions can be define as shell func-
tions with a variant of the functionname syntax,
function.sh.math.nameident ... {list;}
where name is the function name used in the arithmetic expression and each identifier, ident is a name
reference to the long double precision floating point argument. The value of .sh.value when the func-
tion returns is the value of this function. User defined functions can take up to 3 arguments and over-
ride C math library functions.
An internal representation of a variable as a double precision floating point can be specified with the -E [n],
-F [n], or -X [n] option of the typeset special built-in command. The -E option causes the expansion of the
value to be represented using scientific notation when it is expanded. The optional option argument n defines
the number of significant figures. The -F option causes the expansion to be represented as a floating decimal
number when it is expanded. The -X option cause the expansion to be represented using the %a format defined by
ISO C-99. The optional option argument n defines the number of places after the decimal (or radix) point in
this case.
An internal integer representation of a variable can be specified with the -i [n] option of the typeset special
built-in command. The optional option argument n specifies an arithmetic base to be used when expanding the
variable. If you do not specify an arithmetic base, base 10 will be used.
Arithmetic evaluation is performed on the value of each assignment to a variable with the -E, -F, -X, or -i
attribute. Assigning a floating point number to a variable whose type is an integer causes the fractional part
to be truncated.
Prompting.
When used interactively, the shell prompts with the value of PS1 after expanding it for parameter expansion,
command substitution, and arithmetic substitution, before reading a command. In addition, each single ! in
the prompt is replaced by the command number. A !! is required to place ! in the prompt. If at any time a
new-line is typed and further input is needed to complete a command, then the secondary prompt (i.e., the value
of PS2) is issued.
ConditionalExpressions.
A conditionalexpression is used with the [[ compound command to test attributes of files and to compare
strings. Field splitting and file name generation are not performed on the words between [[ and ]]. Each
expression can be constructed from one or more of the following unary or binary expressions:
string True, if string is not null.
-afile
Same as -e below. This is obsolete.
-bfile
True, if file exists and is a block special file.
-cfile
True, if file exists and is a character special file.
-dfile
True, if file exists and is a directory.
-efile
True, if file exists.
-ffile
True, if file exists and is an ordinary file.
-gfile
True, if file exists and it has its setgid bit set.
-kfile
True, if file exists and it has its sticky bit set.
-nstring
True, if length of string is non-zero.
-o?option
True, if option named option is a valid option name.
-ooption
True, if option named option is on.
-pfile
True, if file exists and is a fifo special file or a pipe.
-rfile
True, if file exists and is readable by current process.
-sfile
True, if file exists and has size greater than zero.
-tfildes
True, if file descriptor number fildes is open and associated with a terminal device.
-ufile
True, if file exists and it has its setuid bit set.
-vname
True, if variable name is a valid variable name and is set.
-wfile
True, if file exists and is writable by current process.
-xfile
True, if file exists and is executable by current process. If file exists and is a directory, then true
if the current process has permission to search in the directory.
-zstring
True, if length of string is zero.
-Lfile
True, if file exists and is a symbolic link.
-hfile
True, if file exists and is a symbolic link.
-Nfile
True, if file exists and the modification time is greater than the last access time.
-Ofile
True, if file exists and is owned by the effective user id of this process.
-Gfile
True, if file exists and its group matches the effective group id of this process.
-Rname
True if variable name is a name reference.
-Sfile
True, if file exists and is a socket.
file1-ntfile2
True, if file1 exists and file2 does not, or file1 is newer than file2.
file1-otfile2
True, if file2 exists and file1 does not, or file1 is older than file2.
file1-effile2
True, if file1 and file2 exist and refer to the same file.
string==pattern
True, if string matches pattern. Any part of pattern can be quoted to cause it to be matched as a
string. With a successful match to a pattern, the .sh.match array variable will contain the match and
sub-pattern matches.
string=pattern
Same as == above, but is obsolete.
string!=pattern
True, if string does not match pattern. When the string matches the pattern the .sh.match array vari-
able will contain the match and sub-pattern matches.
string=~ere
True if string matches the pattern ~(E)ere where ere is an extended regular expression.
string1<string2
True, if string1 comes before string2 based on ASCII value of their characters.
string1>string2
True, if string1 comes after string2 based on ASCII value of their characters.
The following obsolete arithmetic comparisons are also permitted:
exp1-eqexp2
True, if exp1 is equal to exp2.
exp1-neexp2
True, if exp1 is not equal to exp2.
exp1-ltexp2
True, if exp1 is less than exp2.
exp1-gtexp2
True, if exp1 is greater than exp2.
exp1-leexp2
True, if exp1 is less than or equal to exp2.
exp1-geexp2
True, if exp1 is greater than or equal to exp2.
In each of the above expressions, if file is of the form /dev/fd/n, where n is an integer, then the test is
applied to the open file whose descriptor number is n.
A compound expression can be constructed from these primitives by using any of the following, listed in
decreasing order of precedence.
(expression)
True, if expression is true. Used to group expressions.
!expression
True if expression is false.
expression1&&expression2
True, if expression1 and expression2 are both true.
expression1||expression2
True, if either expression1 or expression2 is true.
Input/Output.
Before a command is executed, its input and output may be redirected using a special notation interpreted by
the shell. The following may appear anywhere in a simple-command or may precede or follow a command and are
not passed on to the invoked command. Command substitution, parameter expansion, and arithmetic substitution
occur before word or digit is used except as noted below. File name generation occurs only if the shell is
interactive and the pattern matches a single file. Field splitting is not performed.
In each of the following redirections, if file is of the form /dev/sctp/host/port, /dev/tcp/host/port, or
/dev/udp/host/port, where host is a hostname or host address, and port is a service given by name or an integer
port number, then the redirection attempts to make a tcp, sctp or udp connection to the corresponding socket.
No intervening space is allowed between the characters of redirection operators.
<word Use file word as standard input (file descriptor 0).
>word Use file word as standard output (file descriptor 1). If the file does not exist then it is cre-
ated. If the file exists, and the noclobber option is on, this causes an error; otherwise, it is
truncated to zero length.
>|word Same as >, except that it overrides the noclobber option.
>;word Write output to a temporary file. If the command completes successfully rename it to word, oth-
erwise, delete the temporary file. >;word cannot be used with the exec(2). built-in.
>>word Use file word as standard output. If the file exists, then output is appended to it (by first
seeking to the end-of-file); otherwise, the file is created.
<>word Open file word for reading and writing as standard output.
<>;word The same as <>word except that if the command completes successfully, word is truncated to the
offset at command completion. <>;word cannot be used with the exec(2). built-in.
<<[-]word The shell input is read up to a line that is the same as word after any quoting has been removed,
or to an end-of-file. No parameter substitution, command substitution, arithmetic substitution
or file name generation is performed on word. The resulting document, called a here-document,
becomes the standard input. If any character of word is quoted, then no interpretation is placed
upon the characters of the document; otherwise, parameter expansion, command substitution, and
arithmetic substitution occur, \new-line is ignored, and \ must be used to quote the characters
\, $, `. If - is appended to <<, then all leading tabs are stripped from word and from the docu-
ment. If # is appended to <<, then leading spaces and tabs will be stripped off the first line
of the document and up to an equivalent indentation will be stripped from the remaining lines and
from word. A tab stop is assumed to occur at every 8 columns for the purposes of determining the
indentation.
<<<word A short form of here document in which word becomes the contents of the here-document after any
parameter expansion, command substitution, and arithmetic substitution occur.
<&digit The standard input is duplicated from file descriptor digit (see dup(2)). Similarly for the
standard output using >&digit.
<&digit- The file descriptor given by digit is moved to standard input. Similarly for the standard output
using >&digit-.
<&- The standard input is closed. Similarly for the standard output using >&-.
<&p The input from the co-process is moved to standard input.
>&p The output to the co-process is moved to standard output.
<#((expr)) Evaluate arithmetic expression expr and position file descriptor 0 to the resulting value bytes
from the start of the file. The variables CUR and EOF evaluate to the current offset and end-of-
file offset respectively when evaluating expr.>#((offset)) The same as <# except applies to file descriptor 1.
<#pattern Seeks forward to the beginning of the next line containing pattern.
<##pattern The same as <# except that the portion of the file that is skipped is copied to standard output.
If one of the above is preceded by a digit, with no intervening space, then the file descriptor number referred
to is that specified by the digit (instead of the default 0 or 1). If one of the above, other than >&- and the
># and <# forms, is preceded by {varname} with no intervening space, then a file descriptor number > 10 will be
selected by the shell and stored in the variable varname. If >&- or the any of the ># and <# forms is preceded
by {varname} the value of varname defines the file descriptor to close or position. For example:
...2>&1
means file descriptor 2 is to be opened for writing as a duplicate of file descriptor 1 and
exec{n}<file
means open file named file for reading and store the file descriptor number in variable n.
The order in which redirections are specified is significant. The shell evaluates each redirection in terms of
the (filedescriptor, file) association at the time of evaluation. For example:
...1>fname2>&1
first associates file descriptor 1 with file fname. It then associates file descriptor 2 with the file associ-
ated with file descriptor 1 (i.e. fname). If the order of redirections were reversed, file descriptor 2 would
be associated with the terminal (assuming file descriptor 1 had been) and then file descriptor 1 would be asso-
ciated with file fname.
If a command is followed by & and job control is not active, then the default standard input for the command is
the empty file /dev/null. Otherwise, the environment for the execution of a command contains the file descrip-
tors of the invoking shell as modified by input/output specifications.
Environment.
The environment (see environ(7)) is a list of name-value pairs that is passed to an executed program in the
same way as a normal argument list. The names must be identifiers and the values are character strings. The
shell interacts with the environment in several ways. On invocation, the shell scans the environment and cre-
ates a variable for each name found, giving it the corresponding value and attributes and marking it export.
Executed commands inherit the environment. If the user modifies the values of these variables or creates new
ones, using the export or typeset-x commands, they become part of the environment. The environment seen by
any executed command is thus composed of any name-value pairs originally inherited by the shell, whose values
may be modified by the current shell, plus any additions which must be noted in export or typeset-x commands.
The environment for any simple-command or function may be augmented by prefixing it with one or more variable
assignments. A variable assignment argument is a word of the form identifier=value. Thus:
TERM=450cmdargs and
(exportTERM;TERM=450;cmdargs)
are equivalent (as far as the above execution of cmd is concerned except for special built-in commands listed
below - those that are preceded with a dagger).
If the obsolete -k option is set, all variable assignment arguments are placed in the environment, even if they
occur after the command name. The following first prints a=bc and then c:
echoa=bcset-kechoa=bc
This feature is intended for use with scripts written for early versions of the shell and its use in new
scripts is strongly discouraged. It is likely to disappear someday.
Functions.
For historical reasons, there are two ways to define functions, the name() syntax and the functionname syntax,
described in the Commands section above. Shell functions are read in and stored internally. Alias names are
resolved when the function is read. Functions are executed like commands with the arguments passed as posi-
tional parameters. (See Execution below.)
Functions defined by the functionname syntax and called by name execute in the same process as the caller and
share all files and present working directory with the caller. Traps caught by the caller are reset to their
default action inside the function. A trap condition that is not caught or ignored by the function causes the
function to terminate and the condition to be passed on to the caller. A trap on EXIT set inside a function is
executed in the environment of the caller after the function completes. Ordinarily, variables are shared
between the calling program and the function. However, the typeset special built-in command used within a
function defines local variables whose scope includes the current function. They can be passed to functions
that they call in the variable assignment list that precedes the call or as arguments passed as name refer-
ences. Errors within functions return control to the caller.
Functions defined with the name() syntax and functions defined with the functionname syntax that are invoked
with the . special built-in are executed in the caller's environment and share all variables and traps with
the caller. Errors within these function executions cause the script that contains them to abort.
The special built-in command return is used to return from function calls.
Function names can be listed with the -f or +f option of the typeset special built-in command. The text of
functions, when available, will also be listed with -f. Functions can be undefined with the -f option of the
unset special built-in command.
Ordinarily, functions are unset when the shell executes a shell script. Functions that need to be defined
across separate invocations of the shell should be placed in a directory and the FPATH variable should contain
the name of this directory. They may also be specified in the ENV file.
DisciplineFunctions.
Each variable can have zero or more discipline functions associated with it. The shell initially understands
the discipline names get, set, append, and unset but can be added when defining new types. On most systems
others can be added at run time via the C programming interface extension provided by the builtin built-in
utility. If the get discipline is defined for a variable, it is invoked whenever the given variable is refer-
enced. If the variable .sh.value is assigned a value inside the discipline function, the referenced variable
will evaluate to this value instead. If the set discipline is defined for a variable, it is invoked whenever
the given variable is assigned a value. If the append discipline is defined for a variable, it is invoked
whenever a value is appended to the given variable. The variable .sh.value is given the value of the variable
before invoking the discipline, and the variable will be assigned the value of .sh.value after the discipline
completes. If .sh.value is unset inside the discipline, then that value is unchanged. If the unset discipline
is defined for a variable, it is invoked whenever the given variable is unset. The variable will not be unset
unless it is unset explicitly from within this discipline function.
The variable .sh.name contains the name of the variable for which the discipline function is called, .sh.sub-script is the subscript of the variable, and .sh.value will contain the value being assigned inside the set
discipline function. The variable _ is a reference to the variable including the subscript if any. For the
set discipline, changing .sh.value will change the value that gets assigned. Finally, the expansion
${var.name}, when name is the name of a discipline, and there is no variable of this name, is equivalent to the
command substitution ${var.name;}.
NameSpaces.
Commands and functions that are executed as part of the list of a namespace command that modify variables or
create new ones, create a new variable whose name is the name of the name space as given by identifier preceded
by .. When a variable whose name is name is referenced, it is first searched for using .identifier.name. Sim-
ilarly, a function defined by a command in the namespacelist is created using the name space name preceded by
a ..
When the list of a namespace command contains a namespace command, the names of variables and functions that
are created consist of the variable or function name preceded by the list of identifiers each preceded by ..
Outside of a name space, a variable or function created inside a name space can be referenced by preceding it
with the name space name.
By default, variables staring with .sh are in the sh name space.
TypeVariables.
Typed variables provide a way to create data structure and objects. A type can be defined either by a shared
library, by the enum built-in command described below, or by using the new -T option of the typeset built-in
command. With the -T option of typeset, the type name, specified as an option argument to -T, is set with a
compound variable assignment that defines the type. Function definitions can appear inside the compound vari-
able assignment and these become discipline functions for this type and can be invoked or redefined by each
instance of the type. The function name create is treated specially. It is invoked for each instance of the
type that is created but is not inherited and cannot be redefined for each instance.
When a type is defined a special built-in command of that name is added. These built-ins are declaration com-
mands and follow the same expansion rules as all the special built-in commands defined below that are preceded
by ++. These commands can subsequently be used inside further type definitions. The man page for these com-
mands can be generated by using the --man option or any of the other -- options described with getopts. The
-r, -a, -A, -h, and -S options of typeset are permitted with each of these new built-ins.
An instance of a type is created by invoking the type name followed by one or more instance names. Each
instance of the type is initialized with a copy of the sub-variables except for sub-variables that are defined
with the -S option. Variables defined with the -S are shared by all instances of the type. Each instance can
change the value of any sub-variable and can also define new discipline functions of the same names as those
defined by the type definition as well as any standard discipline names. No additional sub-variables can be
defined for any instance.
When defining a type, if the value of a sub-variable is not set and the -r attribute is specified, it causes
the sub-variable to be a required sub-variable. Whenever an instance of a type is created, all required sub-
variables must be specified. These sub-variables become readonly in each instance.
When unset is invoked on a sub-variable within a type, and the -r attribute has not been specified for this
field, the value is reset to the default value associative with the type. Invoking unset on a type instance
not contained within another type deletes all sub-variables and the variable itself.
A type definition can be derived from another type definition by defining the first sub-variable name as _ and
defining its type as the base type. Any remaining definitions will be additions and modifications that apply
to the new type. If the new type name is the same is that of the base type, the type will be replaced and the
original type will no longer be accessible.
The typeset command with the -T and no option argument or operands will write all the type definitions to stan-
dard output in a form that that can be read in to create all they types.
Jobs.
If the monitor option of the set command is turned on, an interactive shell associates a job with each
pipeline. It keeps a table of current jobs, printed by the jobs command, and assigns them small integer num-
bers. When a job is started asynchronously with &, the shell prints a line which looks like:
[1] 1234
indicating that the job which was started asynchronously was job number 1 and had one (top-level) process,
whose process id was 1234.
This paragraph and the next require features that are not in all versions of UNIX and may not apply. If you
are running a job and wish to do something else you may hit the key ^Z (control-Z) which sends a STOP signal to
the current job. The shell will then normally indicate that the job has been 'Stopped', and print another
prompt. You can then manipulate the state of this job, putting it in the background with the bg command, or
run some other commands and then eventually bring the job back into the foreground with the foreground command
fg. A ^Z takes effect immediately and is like an interrupt in that pending output and unread input are dis-
carded when it is typed.
A job being run in the background will stop if it tries to read from the terminal. Background jobs are nor-
mally allowed to produce output, but this can be disabled by giving the command sttytostop. If you set this
tty option, then background jobs will stop when they try to produce output like they do when they try to read
input.
A job pool is a collection of jobs started with list& associated with a name.
There are several ways to refer to jobs in the shell. A job can be referred to by the process id of any pro-
cess of the job or by one of the following:
%number
The job with the given number.
pool All the jobs in the job pool named by pool.
pool.number
The job number number in the job pool named by pool.
%string
Any job whose command line begins with string.
%?string
Any job whose command line contains string.
%% Current job.
%+ Equivalent to %%.
%- Previous job. In addition, unless noted otherwise, wherever a job can be specified, the name of a back-
ground job pool can be used to represent all the jobs in that pool.
The shell learns immediately whenever a process changes state. It normally informs you whenever a job becomes
blocked so that no further progress is possible, but only just before it prints a prompt. This is done so that
it does not otherwise disturb your work. The notify option of the set command causes the shell to print these
job change messages as soon as they occur.
When the monitor option is on, each background job that completes triggers any trap set for CHLD.
When you try to leave the shell while jobs are running or stopped, you will be warned that 'You have
stopped(running) jobs.' You may use the jobs command to see what they are. If you immediately try to exit
again, the shell will not warn you a second time, and the stopped jobs will be terminated. When a login shell
receives a HUP signal, it sends a HUP signal to each job that has not been disowned with the disown built-in
command described below.
Signals.
The INT and QUIT signals for an invoked command are ignored if the command is followed by & and the monitor
option is active. Otherwise, signals have the values inherited by the shell from its parent (but see also the
trap built-in command below).
Execution.
Each time a command is read, the above substitutions are carried out. If the command name matches one of the
SpecialBuilt-inCommands listed below, it is executed within the current shell process. Next, the command
name is checked to see if it matches a user defined function. If it does, the positional parameters are saved
and then reset to the arguments of the function call. A function is also executed in the current shell pro-
cess. When the function completes or issues a return, the positional parameter list is restored. For func-
tions defined with the functionname syntax, any trap set on EXIT within the function is executed. The exit
value of a function is the value of the last command executed. If a command name is not a specialbuilt-incommand or a user defined function, but it is one of the built-in commands listed below, it is executed in the
current shell process.
The shell variables PATH followed by the variable FPATH defines the list of directories to search for the com-
mand name. Alternative directory names are separated by a colon (:). The default path is equal to get-confPATH output. The current directory can be specified by two or more adjacent colons, or by a colon at the
beginning or end of the path list. If the command name contains a /, then the search path is not used. Other-
wise, each directory in the list of directories defined by PATH and FPATH is checked in order. If the direc-
tory being searched is contained in FPATH and contains a file whose name matches the command being searched,
then this file is loaded into the current shell environment as if it were the argument to the . command except
that only preset aliases are expanded, and a function of the given name is executed as described above.
If this directory is not in FPATH the shell first determines whether there is a built-in version of a command
corresponding to a given pathname and if so it is invoked in the current process. If no built-in is found, the
shell checks for a file named .paths in this directory. If found and there is a line of the form FPATH=path
where path names an existing directory then that directory is searched after immediately after the current
directory as if it were found in the FPATH variable. If path does not begin with /, it is checked for relative
to the directory being searched.
The .paths file is then checked for a line of the form PLUGIN_LIB=libname [ :libname ] ... . Each library
named by libname will be searched for as if it were an option argument to builtin-f, and if it contains a
built-in of the specified name this will be executed instead of a command by this name. Any built-in loaded
from a library found this way will be associated with the directory containing the .paths file so it will only
execute if not found in an earlier directory.
Finally, the directory will be checked for a file of the given name. If the file has execute permission but is
not an a.out file, it is assumed to be a file containing shell commands. A separate shell is spawned to read
it. All non-exported variables are removed in this case. If the shell command file doesn't have read permis-
sion, or if the setuid and/or setgid bits are set on the file, then the shell executes an agent whose job it is
to set up the permissions and execute the shell with the shell command file passed down as an open file. If
the .paths contains a line of the form name=value in the first or second line, then the environment variable
name is modified by prepending the directory specified by value to the directory list. If value is not an
absolute directory, then it specifies a directory relative to the directory that the executable was found. If
the environment variable name does not already exist it will be added to the environment list for the specified
command. A parenthesized command is executed in a sub-shell without removing non-exported variables.
CommandRe-entry.
The text of the last HISTSIZE (default 512) commands entered from a terminal device is saved in a history file.
The file $HOME/.sh_history is used if the HISTFILE variable is not set or if the file it names is not writable.
A shell can access the commands of all interactive shells which use the same named HISTFILE. The built-in com-
mand hist is used to list or edit a portion of this file. The portion of the file to be edited or listed can
be selected by number or by giving the first character or characters of the command. A single command or range
of commands can be specified. If you do not specify an editor program as an argument to hist then the value of
the variable HISTEDIT is used. If HISTEDIT is unset, the obsolete variable FCEDIT is used. If FCEDIT is not
defined, then /bin/ed is used. The edited command(s) is printed and re-executed upon leaving the editor unless
you quit without writing. The -s option (and in obsolete versions, the editor name -) is used to skip the
editing phase and to re-execute the command. In this case a substitution parameter of the form old=new can be
used to modify the command before execution. For example, with the preset alias r, which is aliased to ?hist-s?, typing 'rbad=goodc' will re-execute the most recent command which starts with the letter c, replacing
the first occurrence of the string bad with the string good.
In-lineEditingOptions.
Normally, each command line entered from a terminal device is simply typed followed by a new-line ('RETURN' or
'LINE FEED'). If either the emacs, gmacs, or vi option is active, the user can edit the command line. To be
in either of these edit modes set the corresponding option. An editing option is automatically selected each
time the VISUAL or EDITOR variable is assigned a value ending in either of these option names.
The editing features require that the user's terminal accept 'RETURN' as carriage return without line feed and
that a space (' ') must overwrite the current character on the screen.
Unless the multiline option is on, the editing modes implement a concept where the user is looking through a
window at the current line. The window width is the value of COLUMNS if it is defined, otherwise 80. If the
window width is too small to display the prompt and leave at least 8 columns to enter input, the prompt is
truncated from the left. If the line is longer than the window width minus two, a mark is displayed at the end
of the window to notify the user. As the cursor moves and reaches the window boundaries the window will be
centered about the cursor. The mark is a > (<,*) if the line extends on the right (left, both) side(s) of the
window.
The search commands in each edit mode provide access to the history file. Only strings are matched, not pat-
terns, although a leading ^ in the string restricts the match to begin at the first character in the line.
Each of the edit modes has an operation to list the files or commands that match a partially entered word.
When applied to the first word on the line, or the first word after a ;, |, &, or (, and the word does not
begin with ~ or contain a /, the list of aliases, functions, and executable commands defined by the PATH vari-
able that could match the partial word is displayed. Otherwise, the list of files that match the given word is
displayed. If the partially entered word does not contain any file expansion characters, a * is appended
before generating these lists. After displaying the generated list, the input line is redrawn. These opera-
tions are called command name listing and file name listing, respectively. There are additional operations,
referred to as command name completion and file name completion, which compute the list of matching commands or
files, but instead of printing the list, replace the current word with a complete or partial match. For file
name completion, if the match is unique, a / is appended if the file is a directory and a space is appended if
the file is not a directory. Otherwise, the longest common prefix for all the matching files replaces the
word. For command name completion, only the portion of the file names after the last / are used to find the
longest command prefix. If only a single name matches this prefix, then the word is replaced with the command
name followed by a space. When using a tab for completion that does not yield a unique match, a subsequent tab
will provide a numbered list of matching alternatives. A specific selection can be made by entering the selec-
tion number followed by a tab.
KeyBindings.
The KEYBD trap can be used to intercept keys as they are typed and change the characters that are actually seen
by the shell. This trap is executed after each character (or sequence of characters when the first character
is ESC) is entered while reading from a terminal. The variable .sh.edchar contains the character or character
sequence which generated the trap. Changing the value of .sh.edchar in the trap action causes the shell to
behave as if the new value were entered from the keyboard rather than the original value.
The variable .sh.edcol is set to the input column number of the cursor at the time of the input. The variable
.sh.edmode is set to ESC when in vi insert mode (see below) and is null otherwise. By prepending ${.sh.edit-mode} to a value assigned to .sh.edchar it will cause the shell to change to control mode if it is not already
in this mode.
This trap is not invoked for characters entered as arguments to editing directives, or while reading input for
a character search.
EmacsEditingMode.
This mode is entered by enabling either the emacs or gmacs option. The only difference between these two modes
is the way they handle ^T. To edit, the user moves the cursor to the point needing correction and then inserts
or deletes characters or words as needed. All the editing commands are control characters or escape sequences.
The notation for control characters is caret (^) followed by the character. For example, ^F is the notation
for control F. This is entered by depressing 'f' while holding down the 'CTRL' (control) key. The 'SHIFT' key
is not depressed. (The notation ^? indicates the DEL (delete) key.)
The notation for escape sequences is M- followed by a character. For example, M-f (pronounced Meta f) is
entered by depressing ESC (ascii 033) followed by 'f'. (M-F would be the notation for ESC followed by 'SHIFT'
(capital) 'F'.)
All edit commands operate from any place on the line (not just at the beginning). Neither the 'RETURN' nor the
'LINE FEED' key is entered after edit commands except when noted.
^F Move cursor forward (right) one character.
M-[C Move cursor forward (right) one character.
M-f Move cursor forward one word. (The emacs editor's idea of a word is a string of characters consist-
ing of only letters, digits and underscores.)
^B Move cursor backward (left) one character.
M-[D Move cursor backward (left) one character.
M-b Move cursor backward one word.
^A Move cursor to start of line.
M-[H Move cursor to start of line.
^E Move cursor to end of line.
M-[Y Move cursor to end of line.
^]char Move cursor forward to character char on current line.
M-^]char Move cursor backward to character char on current line.
^X^X Interchange the cursor and mark.
erase (User defined erase character as defined by the stty(1) command, usually ^H or #.) Delete previous
character.
lnext (User defined literal next character as defined by the stty(1) command, or ^V if not defined.)
Removes the next character's editing features (if any).
^D Delete current character.
M-d Delete current word.
M-^H (Meta-backspace) Delete previous word.
M-h Delete previous word.
M-^? (Meta-DEL) Delete previous word (if your interrupt character is ^? (DEL, the default) then this com-
mand will not work).
^T Transpose current character with previous character and advance the cursor in emacs mode. Transpose
two previous characters in gmacs mode.
^C Capitalize current character.
M-c Capitalize current word.
M-l Change the current word to lower case.
^K Delete from the cursor to the end of the line. If preceded by a numerical parameter whose value is
less than the current cursor position, then delete from given position up to the cursor. If preceded
by a numerical parameter whose value is greater than the current cursor position, then delete from
cursor up to given cursor position.
^W Kill from the cursor to the mark.
M-p Push the region from the cursor to the mark on the stack.
kill (User defined kill character as defined by the stty command, usually ^G or @.) Kill the entire cur-
rent line. If two kill characters are entered in succession, all kill characters from then on cause
a line feed (useful when using paper terminals).
^Y Restore last item removed from line. (Yank item back to the line.)
^L Line feed and print current line.
M-^L Clear the screen.
^@ (Null character) Set mark.
M-space (Meta space) Set mark.
^J (New line) Execute the current line.
^M (Return) Execute the current line.
eof End-of-file character, normally ^D, is processed as an End-of-file only if the current line is null.
^P Fetch previous command. Each time ^P is entered the previous command back in time is accessed.
Moves back one line when not on the first line of a multi-line command.
M-[A If the cursor is at the end of the line, it is equivalent to ^R with string set to the contents of
the current line. Otherwise, it is equivalent to ^P.M-< Fetch the least recent (oldest) history line.
M-> Fetch the most recent (youngest) history line.
^N Fetch next command line. Each time ^N is entered the next command line forward in time is accessed.
M-[B Equivalent to ^N.^Rstring Reverse search history for a previous command line containing string. If a parameter of zero is
given, the search is forward. String is terminated by a 'RETURN' or 'NEW LINE'. If string is pre-
ceded by a ^, the matched line must begin with string. If string is omitted, then the next command
line containing the most recent string is accessed. In this case a parameter of zero reverses the
direction of the search.
^O Operate - Execute the current line and fetch the next line relative to current line from the history
file.
M-digits (Escape) Define numeric parameter, the digits are taken as a parameter to the next command. The com-
mands that accept a parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-., M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
M-letter Soft-key - Your alias list is searched for an alias by the name _letter and if an alias of this name
is defined, its value will be inserted on the input queue. The letter must not be one of the above
meta-functions.
M-[letter Soft-key - Your alias list is searched for an alias by the name __letter and if an alias of this name
is defined, its value will be inserted on the input queue. This can be used to program function keys
on many terminals.
M-. The last word of the previous command is inserted on the line. If preceded by a numeric parameter,
the value of this parameter determines which word to insert rather than the last word.
M-_ Same as M-..
M-* Attempt file name generation on the current word. An asterisk is appended if the word doesn't match
any file or contain any special pattern characters.
M-ESC Command or file name completion as described above.
^Itab Attempts command or file name completion as described above. If a partial completion occurs, repeat-
ing this will behave as if M-= were entered. If no match is found or entered after space, a tab is
inserted.
M-= If not preceded by a numeric parameter, it generates the list of matching commands or file names as
described above. Otherwise, the word under the cursor is replaced by the item corresponding to the
value of the numeric parameter from the most recently generated command or file list. If the cursor
is not on a word, it is inserted instead.
^U Multiply parameter of next command by 4.
\ Escape next character. Editing characters, the user's erase, kill and interrupt (normally ^?) char-
acters may be entered in a command line or in a search string if preceded by a \. The \ removes the
next character's editing features (if any).
M-^V Display version of the shell.
M-# If the line does not begin with a #, a # is inserted at the beginning of the line and after each new-
line, and the line is entered. This causes a comment to be inserted in the history file. If the
line begins with a #, the # is deleted and one # after each new-line is also deleted.
ViEditingMode.
There are two typing modes. Initially, when you enter a command you are in the input mode. To edit, the user
enters control mode by typing ESC (033) and moves the cursor to the point needing correction and then inserts
or deletes characters or words as needed. Most control commands accept an optional repeat count prior to the
command.
When in vi mode on most systems, canonical processing is initially enabled and the command will be echoed again
if the speed is 1200 baud or greater and it contains any control characters or less than one second has elapsed
since the prompt was printed. The ESC character terminates canonical processing for the remainder of the com-
mand and the user can then modify the command line. This scheme has the advantages of canonical processing
with the type-ahead echoing of raw mode.
If the option viraw is also set, the terminal will always have canonical processing disabled. This mode is
implicit for systems that do not support two alternate end of line delimiters, and may be helpful for certain
terminals.
InputEditCommands
By default the editor is in input mode.
erase (User defined erase character as defined by the stty command, usually ^H or #.) Delete previ-
ous character.
^W Delete the previous blank separated word. On some systems the viraw option may be required
for this to work.
eof As the first character of the line causes the shell to terminate unless the ignoreeof option
is set. Otherwise this character is ignored.
lnext (User defined literal next character as defined by the stty(1) or ^V if not defined.) Removes
the next character's editing features (if any). On some systems the viraw option may be
required for this to work.
\ Escape the next erase or kill character.
^Itab Attempts command or file name completion as described above and returns to input mode. If a
partial completion occurs, repeating this will behave as if = were entered from control mode.
If no match is found or entered after space, a tab is inserted.
MotionEditCommands
These commands will move the cursor.
[count]l Cursor forward (right) one character.
[count][C Cursor forward (right) one character.
[count]w Cursor forward one alpha-numeric word.
[count]W Cursor to the beginning of the next word that follows a blank.
[count]e Cursor to end of word.
[count]E Cursor to end of the current blank delimited word.
[count]h Cursor backward (left) one character.
[count][D Cursor backward (left) one character.
[count]b Cursor backward one word.
[count]B Cursor to preceding blank separated word.
[count]| Cursor to column count.
[count]fc Find the next character c in the current line.
[count]Fc Find the previous character c in the current line.
[count]tc Equivalent to f followed by h.
[count]Tc Equivalent to F followed by l.
[count]; Repeats count times, the last single character find command, f, F, t, or T.
[count], Reverses the last single character find command count times.
0 Cursor to start of line.
^ Cursor to start of line.
[H Cursor to first non-blank character in line.
$ Cursor to end of line.
[Y Cursor to end of line.
% Moves to balancing (, ), {, }, [, or ]. If cursor is not on one of the above characters, the
remainder of the line is searched for the first occurrence of one of the above characters
first.
SearchEditCommands
These commands access your command history.
[count]k Fetch previous command. Each time k is entered the previous command back in time is accessed.
[count]- Equivalent to k.
[count][A If cursor is at the end of the line it is equivalent to / with string^settothecontentsofthecurrentline. Otherwise, it is equivalent to k.
[count]j Fetch next command. Each time j is entered the next command forward in time is accessed.
[count]+ Equivalent to j.
[count][B Equivalent to j.
[count]G The command number count is fetched. The default is the least recent history command.
/string Search backward through history for a previous command containing string. String is termi-
nated by a 'RETURN' or 'NEW LINE'. If string is preceded by a ^, the matched line must begin
with string. If string is null, the previous string will be used.
?string Same as / except that search will be in the forward direction.
n Search for next match of the last pattern to / or ? commands.
N Search for next match of the last pattern to / or ?, but in reverse direction.
TextModificationEditCommands
These commands will modify the line.
a Enter input mode and enter text after the current character.
A Append text to the end of the line. Equivalent to $a.
[count]cmotionc[count]motion
Delete current character through the character that motion would move the cursor to and enter
input mode. If motion is c, the entire line will be deleted and input mode entered.
C Delete the current character through the end of line and enter input mode. Equivalent to c$.
S Equivalent to cc.
[count]s Replace characters under the cursor in input mode.
D Delete the current character through the end of line. Equivalent to d$.
[count]dmotiond[count]motion
Delete current character through the character that motion would move to. If motion is d,
the entire line will be deleted.
i Enter input mode and insert text before the current character.
I Insert text before the beginning of the line. Equivalent to 0i.
[count]P Place the previous text modification before the cursor.
[count]p Place the previous text modification after the cursor.
R Enter input mode and replace characters on the screen with characters you type overlay fash-
ion.
[count]rc Replace the count character(s) starting at the current cursor position with c, and advance the
cursor.
[count]x Delete current character.
[count]X Delete preceding character.
[count]. Repeat the previous text modification command.
[count]~ Invert the case of the count character(s) starting at the current cursor position and advance
the cursor.
[count]_ Causes the count word of the previous command to be appended and input mode entered. The last
word is used if count is omitted.
* Causes an * to be appended to the current word and file name generation attempted. If no
match is found, it rings the bell. Otherwise, the word is replaced by the matching pattern
and input mode is entered.
\ Command or file name completion as described above.
OtherEditCommands
Miscellaneous commands.
[count]ymotiony[count]motion
Yank current character through character that motion would move the cursor to and puts them
into the delete buffer. The text and cursor are unchanged.
yy Yanks the entire line.
Y Yanks from current position to end of line. Equivalent to y$.
u Undo the last text modifying command.
U Undo all the text modifying commands performed on the line.
[count]v Returns the command hist-e${VISUAL:-${EDITOR:-vi}}count in the input buffer. If count is
omitted, then the current line is used.
^L Line feed and print current line. Has effect only in control mode.
^J (New line) Execute the current line, regardless of mode.
^M (Return) Execute the current line, regardless of mode.
# If the first character of the command is a #, then this command deletes this # and each # that
follows a newline. Otherwise, sends the line after inserting a # in front of each line in the
command. Useful for causing the current line to be inserted in the history as a comment and
uncommenting previously commented commands in the history file.
[count]= If count is not specified, it generates the list of matching commands or file names as
described above. Otherwise, the word under the the cursor is replaced by the count item from
the most recently generated command or file list. If the cursor is not on a word, it is
inserted instead.
@letter Your alias list is searched for an alias by the name _letter and if an alias of this name is
defined, its value will be inserted on the input queue for processing.
^V Display version of the shell.
Built-inCommands.
The following simple-commands are executed in the shell process. Input/Output redirection is permitted.
Unless otherwise indicated, the output is written on file descriptor 1 and the exit status, when there is no
syntax error, is zero. Except for :, true, false, echo, newgrp, and login, all built-in commands accept -- to
indicate end of options. They also interpret the option --man as a request to display the man page onto stan-
dard error and -? as a help request which prints a usage message on standard error. Commands that are pre-
ceded by one or two + symbols are special built-in commands and are treated specially in the following ways:
1. Variable assignment lists preceding the command remain in effect when the command completes.
2. I/O redirections are processed after variable assignments.
3. Errors cause a script that contains them to abort.
4. They are not valid function names.
5. Words following a command preceded by ++ that are in the format of a variable assignment are expanded
with the same rules as a variable assignment. This means that tilde substitution is performed after the
= sign and field splitting and file name generation are not performed. These are called declaration
built-ins.
+ : [ arg ... ]
The command only expands parameters.
+ .name[arg...]
If name is a function defined with the functionname reserved word syntax, the function is executed in
the current environment (as if it had been defined with the name() syntax.) Otherwise if name refers to
a file, the file is read in its entirety and the commands are executed in the current shell environment.
The search path specified by PATH is used to find the directory containing the file. If any arguments
arg are given, they become the positional parameters while processing the . command and the original
positional parameters are restored upon completion. Otherwise the positional parameters are unchanged.
The exit status is the exit status of the last command executed.
++ alias [ -ptx ] [ name[ =value ] ] ...
alias with no arguments prints the list of aliases in the form name=value on standard output. The -p
option causes the word alias to be inserted before each one. When one or more arguments are given, an
alias is defined for each name whose value is given. A trailing space in value causes the next word to
be checked for alias substitution. The obsolete -t option is used to set and list tracked aliases. The
value of a tracked alias is the full pathname corresponding to the given name. The value becomes unde-
fined when the value of PATH is reset but the alias remains tracked. Without the -t option, for each
name in the argument list for which no value is given, the name and value of the alias is printed. The
obsolete -x option has no effect. The exit status is non-zero if a name is given, but no value, and no
alias has been defined for the name.
bg [ job... ]
This command is only on systems that support job control. Puts each specified job into the background.
The current job is put in the background if job is not specified. See Jobs for a description of the
format of job.
+ break [ n ]
Exit from the enclosing for, while, until, or select loop, if any. If n is specified, then break n lev-
els.
builtin [ -ds ] [ -ffile ] [ name ... ]
If name is not specified, and no -f option is specified, the built-ins are printed on standard output.
The -s option prints only the special built-ins. Otherwise, each name represents the pathname whose
basename is the name of the built-in. The entry point function name is determined by prepending b_ to
the built-in name. A built-in specified by a pathname will only be executed when that pathname would be
found during the path search. Built-ins found in libraries loaded via the .paths file will be associate
with the pathname of the directory containing the .paths file.
The ISO C/C++ prototype is b_mycommand(intargc, char*argv[], void*context) for the builtin command mycommand
where argv is array an of argc elements and context is an optional pointer to a Shell_t structure as described
in <ast/shell.h>.
Special built-ins cannot be bound to a pathname or deleted. The -d option deletes each of the given built-ins.
On systems that support dynamic loading, the -f option names a shared library containing the code for built-
ins. The shared library prefix and/or suffix, which depend on the system, can be omitted. Once a library is
loaded, its symbols become available for subsequent invocations of builtin. Multiple libraries can be speci-
fied with separate invocations of the builtin command. Libraries are searched in the reverse order in which
they are specified. When a library is loaded, it looks for a function in the library whose name is lib_init()
and invokes this function with an argument of 0.
cd [ -LP ] [ arg ]
cd [ -LP ] oldnew
This command can be in either of two forms. In the first form it changes the current directory to arg.
If arg is - the directory is changed to the previous directory. The shell variable HOME is the default
arg. The variable PWD is set to the current directory. The shell variable CDPATH defines the search
path for the directory containing arg. Alternative directory names are separated by a colon (:). The
default path is <null> (specifying the current directory). Note that the current directory is specified
by a null path name, which can appear immediately after the equal sign or between the colon delimiters
anywhere else in the path list. If arg begins with a / then the search path is not used. Otherwise,
each directory in the path is searched for arg.
The second form of cd substitutes the string new for the string old in the current directory name, PWD,
and tries to change to this new directory.
By default, symbolic link names are treated literally when finding the directory name. This is equiva-
lent to the -L option. The -P option causes symbolic links to be resolved when determining the direc-
tory. The last instance of -L or -P on the command line determines which method is used.
The cd command may not be executed by rksh.rksh93.command [ -pvxV ] name [ arg ... ]
Without the -v or -V options, command executes name with the arguments given by arg. The -p option
causes a default path to be searched rather than the one defined by the value of PATH. Functions will
not be searched for when finding name. In addition, if name refers to a special built-in, none of the
special properties associated with the leading daggers will be honored. (For example, the predefined
alias redirect=?commandexec? prevents a script from terminating when an invalid redirection is given.)
With the -x option, if command execution would result in a failure because there are too many arguments,
errno E2BIG, the shell will invoke command name multiple times with a subset of the arguments on each
invocation. Arguments that occur prior to the first word that expands to multiple arguments and after
the last word that expands to multiple arguments will be passed on each invocation. The exit status
will be the maximum invocation exit status. With the -v option, command is equivalent to the built-in
whence command described below. The -V option causes command to act like whence-v.
+ continue [ n ]
Resume the next iteration of the enclosing for, while, until, or select loop. If n is specified, then
resume at the n-th enclosing loop.
disown [ job... ]
Causes the shell not to send a HUP signal to each given job, or all active jobs if job is omitted, when
a login shell terminates.
echo [ arg ... ]
When the first arg does not begin with a -, and none of the arguments contain a \, then echo prints each
of its arguments separated by a space and terminated by a new-line. Otherwise, the behavior of echo is
system dependent and print or printf described below should be used. See echo(1) for usage and descrip-
tion.
++ enum [ -i ] type[=(value ...) ]
Creates a declaration command named type that is an integer type that allows one of the specified values
as enumeration names. If =(value...) is omitted, then type must be an indexed array variable with at
least two elements and the values are taken from this array variable. If -i is specified the values are
case insensitive.
+ eval [ arg ... ]
The arguments are read as input to the shell and the resulting command(s) executed.
+ exec [ -c ] [ -aname ] [ arg ... ]
If arg is given, the command specified by the arguments is executed in place of this shell without cre-
ating a new process. The -c option causes the environment to be cleared before applying variable
assignments associated with the exec invocation. The -a option causes name rather than the first arg,
to become argv[0] for the new process. Input/output arguments may appear and affect the current pro-
cess. If arg is not given, the effect of this command is to modify file descriptors as prescribed by
the input/output redirection list. In this case, any file descriptor numbers greater than 2 that are
opened with this mechanism are closed when invoking another program.
+ exit [ n ]
Causes the shell to exit with the exit status specified by n. The value will be the least significant 8
bits of the specified status. If n is omitted, then the exit status is that of the last command exe-
cuted. An end-of-file will also cause the shell to exit except for a shell which has the ignoreeof
option (see set below) turned on.
++ export [ -p ] [ name[=value] ] ...
If name is not given, the names and values of each variable with the export attribute are printed with
the values quoted in a manner that allows them to be re-input. The export command is the same as type-set-x except that if you use export within a function, no local variable is created. The -p option
causes the word export to be inserted before each one. Otherwise, the given names are marked for auto-
matic export to the environment of subsequently-executed commands.
false Does nothing, and exits 1. Used with until for infinite loops.
fg [ job... ]
This command is only on systems that support job control. Each job specified is brought to the fore-
ground and waited for in the specified order. Otherwise, the current job is brought into the fore-
ground. See Jobs for a description of the format of job.
getconf [ name [ pathname ] ]
Prints the current value of the configuration parameter given by name. The configuration parameters are
defined by the IEEE POSIX 1003.1 and IEEE POSIX 1003.2 standards. (See pathconf(2) and sysconf(2).)
The pathname argument is required for parameters whose value depends on the location in the file system.
If no arguments are given, getconf prints the names and values of the current configuration parameters.
The pathname / is used for each of the parameters that requires pathname.
getopts [ -aname ] optstringvname [ arg ... ]
Checks arg for legal options. If arg is omitted, the positional parameters are used. An option argu-
ment begins with a + or a -. An option not beginning with + or - or the argument -- ends the options.
Options beginning with + are only recognized when optstring begins with a +. optstring contains the
letters that getopts recognizes. If a letter is followed by a :, that option is expected to have an
argument. The options can be separated from the argument by blanks. The option -? causes getopts to
generate a usage message on standard error. The -a argument can be used to specify the name to use for
the usage message, which defaults to $0.
getopts places the next option letter it finds inside variable vname each time it is invoked. The
option letter will be prepended with a + when arg begins with a +. The index of the next arg is stored
in OPTIND. The option argument, if any, gets stored in OPTARG.
A leading : in optstring causes getopts to store the letter of an invalid option in OPTARG, and to set
vname to ? for an unknown option and to : when a required option argument is missing. Otherwise,
getopts prints an error message. The exit status is non-zero when there are no more options.
There is no way to specify any of the options :, +, -, ?, [, and ]. The option # can only be specified
as the first option.
hist [ -eename ] [ -nlr ] [ first [ last ] ]
hist-s [ old=new ] [ command ]
In the first form, a range of commands from first to last is selected from the last HISTSIZE commands
that were typed at the terminal. The arguments first and last may be specified as a number or as a
string. A string is used to locate the most recent command starting with the given string. A negative
number is used as an offset to the current command number. If the -l option is selected, the commands
are listed on standard output. Otherwise, the editor program ename is invoked on a file containing
these keyboard commands. If ename is not supplied, then the value of the variable HISTEDIT is used. If
HISTEDIT is not set, then FCEDIT (default /bin/ed) is used as the editor. When editing is complete, the
edited command(s) is executed if the changes have been saved. If last is not specified, then it will be
set to first. If first is not specified, the default is the previous command for editing and -16 for
listing. The option -r reverses the order of the commands and the option -n suppresses command numbers
when listing. In the second form, command is interpreted as first described above and defaults to the
last command executed. The resulting command is executed after the optional substitution old=new is
performed.
jobs [ -lnp ] [ job ... ]
Lists information about each given job; or all active jobs if job is omitted. The -l option lists pro-
cess ids in addition to the normal information. The -n option only displays jobs that have stopped or
exited since last notified. The -p option causes only the process group to be listed. See Jobs for a
description of the format of job.
kill [ -ssigname ] job ...
kill [ -nsignum ] job ...
kill-Ll [ sig ... ]
Sends either the TERM (terminate) signal or the specified signal to the specified jobs or processes.
Signals are either given by number with the -n option or by name with the -s option (as given in <sig-nal.h>, stripped of the prefix ''SIG'' with the exception that SIGCLD is named CHLD). For backward com-
patibility, the n and s can be omitted and the number or name placed immediately after the -. If the
signal being sent is TERM (terminate) or HUP (hangup), then the job or process will be sent a CONT (con-
tinue) signal if it is stopped. The argument job can be the process id of a process that is not a mem-
ber of one of the active jobs. See Jobs for a description of the format of job. In the third form,
kill-l, or kill-L, if sig is not specified, the signal names are listed. The -l option list only the
signal names. -L options lists each signal name and corresponding number. Otherwise, for each sig that
is a name, the corresponding signal number is listed. For each sig that is a number, the signal name
corresponding to the least significant 8 bits of sig is listed.
letarg ...
Each arg is a separate arithmeticexpression to be evaluated. let only recognizes octal constants
starting with 0 when the set option letoctal is on. See ArithmeticEvaluation above, for a description
of arithmetic expression evaluation.
The exit status is 0 if the value of the last expression is non-zero, and 1 otherwise.
+ newgrp [ arg ... ]
Equivalent to exec/bin/newgrparg ....
print [ -CRenprsv ] [ -uunit] [ -fformat ] [ arg ... ]
With no options or with option - or --, each arg is printed on standard output. The -f option causes
the arguments to be printed as described by printf. In this case, any e, n, r, R options are ignored.
Otherwise, unless the -C, -R, -r, or -v are specified, the following escape conventions will be applied:
\a The alert character (ascii 07).
\b The backspace character (ascii 010).
\c Causes print to end without processing more arguments and not adding a new-line.
\f The formfeed character (ascii 014).
\n The new-line character (ascii 012).
\r The carriage return character (ascii 015).
\t The tab character (ascii 011).
\v The vertical tab character (ascii 013).
\E The escape character (ascii 033).
\\ The backslash character \.
\0x The character defined by the 1, 2, or 3-digit octal string given by x.
The -R option will print all subsequent arguments and options other than -n. The -e causes the above
escape conventions to be applied. This is the default behavior. It reverses the effect of an earlier
-r. The -p option causes the arguments to be written onto the pipe of the process spawned with |&
instead of standard output. The -v option treats each arg as a variable name and writes the value in
the printf%B format. The -C option treats each arg as a variable name and writes the value in the
printf%#B format. The -s option causes the arguments to be written onto the history file instead of
standard output. The -u option can be used to specify a one digit file descriptor unit number unit on
which the output will be placed. The default is 1. If the option -n is used, no new-line is added to
the output.
printfformat [ arg ... ]
The arguments arg are printed on standard output in accordance with the ANSI-C formatting rules associ-
ated with the format string format. If the number of arguments exceeds the number of format specifica-
tions, the format string is reused to format remaining arguments. The following extensions can also be
used:
%b A %b format can be used instead of %s to cause escape sequences in the corresponding arg to be
expanded as described in print.%B A %B option causes each of the arguments to be treated as variable names and the binary value of
variable will be printed. The alternate flag # causes a compound variable to be output on a sin-
gle line. This is most useful for compound variables and variables whose attribute is -b.
%H A %H format can be used instead of %s to cause characters in arg that are special in HTML and XML
to be output as their entity name. The alternate flag # formats the output for use as a URI.
%P A %P format can be used instead of %s to cause arg to be interpreted as an extended regular
expression and be printed as a shell pattern.
%R A %R format can be used instead of %s to cause arg to be interpreted as a shell pattern and to be
printed as an extended regular expression.
%q A %q format can be used instead of %s to cause the resulting string to be quoted in a manner than
can be reinput to the shell. When q is preceded by the alternative format specifier, #, the
string is quoted in manner suitable as a field in a .csv format file.
%(date-format)T
A %(date-format)T format can be use to treat an argument as a date/time string and to format the
date/time according to the date-format as defined for the date(1) command.
%Z A %Z format will output a byte whose value is 0.
%d The precision field of the %d format can be followed by a . and the output base. In this case,
the # flag character causes base# to be prepended.
# The # flag, when used with the %d format without an output base, displays the output in powers of
1000 indicated by one of the following suffixes: kMGTPE, and when used with the %i format
displays the output in powers of 1024 indicated by one of the following suffixes: KiMiGiTiPiEi.
= The = flag centers the output within the specified field width.
L The L flag, when used with the %c or %s formats, treats precision as character width instead of
byte count.
, The , flag, when used with the %d or %f formats, separates groups of digits with the grouping
delimiter (, on groups of 3 in the C locale.)
pwd [ -LP ]
Outputs the value of the current working directory. The -L option is the default; it prints the logical
name of the current directory. If the -P option is given, all symbolic links are resolved from the
name. The last instance of -L or -P on the command line determines which method is used.
read [ -ACSprsv ] [ -ddelim] [ -nn] [ [ -Nn] [ [ -ttimeout] [ -uunit] [ vname?prompt ] [ vname ... ]
The shell input mechanism. One line is read and is broken up into fields using the characters in IFS as
separators. The escape character, \, is used to remove any special meaning for the next character and
for line continuation. The -d option causes the read to continue to the first character of delim rather
than new-line. The -n option causes at most n bytes to read rather a full line but will return when
reading from a slow device as soon as any characters have been read. The -N option causes exactly n to
be read unless an end-of-file has been encountered or the read times out because of the -t option. In
raw mode, -r, the \ character is not treated specially. The first field is assigned to the first vname,
the second field to the second vname, etc., with leftover fields assigned to the last vname. When vname
has the binary attribute and -n or -N is specified, the bytes that are read are stored directly into the
variable. If the -v is specified, then the value of the first vname will be used as a default value
when reading from a terminal device. The -A option causes the variable vname to be unset and each field
that is read to be stored in successive elements of the indexed array vname. The -C option causes the
variable vname to be read as a compound variable. Blanks will be ignored when finding the beginning
open parenthesis. The -S option causes the line to be treated like a record in a .csv format file so
that double quotes can be used to allow the delimiter character and the new-line character to appear
within a field. The -p option causes the input line to be taken from the input pipe of a process
spawned by the shell using |&. If the -s option is present, the input will be saved as a command in the
history file. The option -u can be used to specify a one digit file descriptor unit unit to read from.
The file descriptor can be opened with the exec special built-in command. The default value of unit n
is 0. The option -t is used to specify a timeout in seconds when reading from a terminal or pipe. If
vname is omitted, then REPLY is used as the default vname. An end-of-file with the -p option causes
cleanup for this process so that another can be spawned. If the first argument contains a ?, the
remainder of this word is used as a prompt on standard error when the shell is interactive. The exit
status is 0 unless an end-of-file is encountered or read has timed out.
++ readonly [ -p ] [ vname[=value] ] ...
If vname is not given, the names and values of each variable with the readonly attribute is printed with
the values quoted in a manner that allows them to be re-inputted. The -p option causes the word read-only to be inserted before each one. Otherwise, the given vnames are marked readonly and these names
cannot be changed by subsequent assignment. When defining a type, if the value of a readonly sub-vari-
able is not defined the value is required when creating each instance.
+ return [ n ]
Causes a shell function or . script to return to the invoking script with the exit status specified by
n. The value will be the least significant 8 bits of the specified status. If n is omitted, then the
return status is that of the last command executed. If return is invoked while not in a function or a .
script, then it behaves the same as exit.
+ set [ ?BCGabefhkmnoprstuvx ] [ ?o [ option ] ] ... [ ?Avname ] [ arg ... ]
The options for this command have meaning as follows:
-A Array assignment. Unset the variable vname and assign values sequentially from the arg list.
If +A is used, the variable vname is not unset first.
-B Enable brace pattern field generation. This is the default behavior.
-B Enable brace group expansion. On by default.
-C Prevents redirection > from truncating existing files. Files that are created are opened with
the O_EXCL mode. Requires >| to truncate a file when turned on.
-G Causes the pattern ** by itself to match files and zero or more directories and sub-directories
when used for file name generation. If followed by a / only directories and sub-directories are
matched.
-a All subsequent variables that are defined are automatically exported.
-b Prints job completion messages as soon as a background job changes state rather than waiting for
the next prompt.
-e Unless contained in a || or && command, or the command following an ifwhile or until command or
in the pipeline following !, if a command has a non-zero exit status, execute the ERR trap, if
set, and exit. This mode is disabled while reading profiles.
-f Disables file name generation.
-h Each command becomes a tracked alias when first encountered.
-k (Obsolete). All variable assignment arguments are placed in the environment for a command, not
just those that precede the command name.
-m Background jobs will run in a separate process group and a line will print upon completion. The
exit status of background jobs is reported in a completion message. On systems with job con-
trol, this option is turned on automatically for interactive shells.
-n Read commands and check them for syntax errors, but do not execute them. Ignored for interac-
tive shells.
-o The following argument can be one of the following option names:
allexport
Same as -a.
errexit Same as -e.
bgnice All background jobs are run at a lower priority. This is the default mode.
braceexpand
Same as -B.
emacs Puts you in an emacs style in-line editor for command entry.
globstar
Same as -G.
gmacs Puts you in a gmacs style in-line editor for command entry.
ignoreeof
The shell will not exit on end-of-file. The command exit must be used.
keyword Same as -k.
letoctal
The let command allows octal constants starting with 0.
markdirs
All directory names resulting from file name generation have a trailing / appended.
monitor Same as -m.
multiline
The built-in editors will use multiple lines on the screen for lines that are longer
than the width of the screen. This may not work for all terminals.
noclobber
Same as -C.
noexec Same as -n.
noglob Same as -f.
nolog Do not save function definitions in the history file.
notify Same as -b.
nounset Same as -u.
pipefail
A pipeline will not complete until all components of the pipeline have completed, and
the return value will be the value of the last non-zero command to fail or zero if no
command has failed.
showme When enabled, simple commands or pipelines preceded by a semicolon (;) will be displayed
as if the xtrace option were enabled but will not be executed. Otherwise, the leading ;
will be ignored.
privileged
Same as -p.
verbose Same as -v.
trackall
Same as -h.
vi Puts you in insert mode of a vi style in-line editor until you hit the escape character
033. This puts you in control mode. A return sends the line.
viraw Each character is processed as it is typed in vi mode.
xtrace Same as -x.
If no option name is supplied, then the current option settings are printed.
-p Disables processing of the $HOME/.profile file and uses the file /etc/suid_profile instead of
the ENV file. This mode is on whenever the effective uid (gid) is not equal to the real uid
(gid). Turning this off causes the effective uid and gid to be set to the real uid and gid.
-r Enables the restricted shell. This option cannot be unset once set.
-s Sort the positional parameters lexicographically.
-t (Obsolete). Exit after reading and executing one command.
-u Treat unset parameters as an error when substituting.
-v Print shell input lines as they are read.
-x Print commands and their arguments as they are executed.
-- Do not change any of the options; useful in setting $1 to a value beginning with -. If no argu-
ments follow this option then the positional parameters are unset.
As an obsolete feature, if the first arg is - then the -x and -v options are turned off and the next arg
is treated as the first argument. Using + rather than - causes these options to be turned off. These
options can also be used upon invocation of the shell. The current set of options may be found in $-.
Unless -A is specified, the remaining arguments are positional parameters and are assigned, in order, to
$1$2 .... If no arguments are given, then the names and values of all variables are printed on the
standard output.
+ shift [ n ]
The positional parameters from $n+1 ... are renamed $1 ... , default n is 1. The parameter n can be
any arithmetic expression that evaluates to a non-negative number less than or equal to $#.
sleepseconds
Suspends execution for the number of decimal seconds or fractions of a second given by seconds.
+ trap [ -p ] [ action ] [ sig ] ...
The -p option causes the trap action associated with each trap as specified by the arguments to be
printed with appropriate quoting. Otherwise, action will be processed as if it were an argument to eval
when the shell receives signal(s) sig. Each sig can be given as a number or as the name of the signal.
Trap commands are executed in order of signal number. Any attempt to set a trap on a signal that was
ignored on entry to the current shell is ineffective. If action is omitted and the first sig is a num-
ber, or if action is -, then the trap(s) for each sig are reset to their original values. If action is
the null string then this signal is ignored by the shell and by the commands it invokes. If sig is ERR
then action will be executed whenever a command has a non-zero exit status. If sig is DEBUG then action
will be executed before each command. The variable .sh.command will contain the contents of the current
command line when action is running. If the exit status of the trap is 2 the command will not be exe-
cuted. If the exit status of the trap is 255 and inside a function or a dot script, the function or dot
script will return. If sig is 0 or EXIT and the trap statement is executed inside the body of a func-
tion defined with the functionname syntax, then the command action is executed after the function com-
pletes. If sig is 0 or EXIT for a trap set outside any function then the command action is executed on
exit from the shell. If sig is KEYBD, then action will be executed whenever a key is read while in
emacs, gmacs, or vi mode. The trap command with no arguments prints a list of commands associated with
each signal number.
An exit or return without an argument in a trap action will preserve the exit status of the command that
invoked the trap.
true Does nothing, and exits 0. Used with while for infinite loops.
++ typeset [ ?ACHSfblmnprtux ] [ ?EFLRXZi[n]][+-M[mapname]][-T[tname=(assign_list)]][-hstr][-a[type]][vname[=value]]...
Sets attributes and values for shell variables and functions. When invoked inside a function defined
with the functionname syntax, a new instance of the variable vname is created, and the variable's value
and type are restored when the function completes. The following list of attributes may be specified:
-A Declares vname to be an associative array. Subscripts are strings rather than arithmetic expres-
sions.
-C causes each vname to be a compound variable. value names a compound variable it is copied into
vname. Otherwise, it unsets each vname.
-a Declares vname to be an indexed array. If type is specified, it must be the name of an enumera-
tion type created with the enum command and it allows enumeration constants to be used as sub-
scripts.
-E Declares vname to be a double precision floating point number. If n is non-zero, it defines the
number of significant figures that are used when expanding vname. Otherwise, ten significant
figures will be used.
-F Declares vname to be a double precision floating point number. If n is non-zero, it defines the
number of places after the decimal point that are used when expanding vname. Otherwise ten
places after the decimal point will be used.
-H This option provides UNIX to host-name file mapping on non-UNIX machines.
-L Left justify and remove leading blanks from value. If n is non-zero, it defines the width of the
field, otherwise it is determined by the width of the value of first assignment. When the vari-
able is assigned to, it is filled on the right with blanks or truncated, if necessary, to fit
into the field. The -R option is turned off.
-M Use the character mapping mapping defined by wctrans(3). such as tolower and toupper when
assigning a value to each of the specified operands. When mapping is specified and there are not
operands, all variables that use this mapping are written to standard output. When mapping is
omitted and there are no operands, all mapped variables are written to standard output.
-R Right justify and fill with leading blanks. If n is non-zero, it defines the width of the field,
otherwise it is determined by the width of the value of first assignment. The field is left
filled with blanks or truncated from the end if the variable is reassigned. The -L option is
turned off.
-S When used within the assign_list of a type definition, it causes the specified sub-variable to be
shared by all instances of the type. When used inside a function defined with the function
reserved word, the specified variables will have functionstatic scope. Otherwise, the variable
is unset prior to processing the assignment list.
-T If followed by tname, it creates a type named by tname using the compound assignment assign_list
to tname. Otherwise, it writes all the type definitions to standard output.
-X Declares vname to be a double precision floating point number and expands using the %a format of
ISO-C99. If n is non-zero, it defines the number of hex digits after the radix point that is
used when expanding vname. The default is 10.
-Z Right justify and fill with leading zeros if the first non-blank character is a digit and the -L
option has not been set. Remove leading zeros if the -L option is also set. If n is non-zero,
it defines the width of the field, otherwise it is determined by the width of the value of first
assignment.
-f The names refer to function names rather than variable names. No assignments can be made and the
only other valid options are -S, -t, -u and -x. The -S can be used with discipline functions
defined in a type to indicate that the function is static. For a static function, the same
method will be used by all instances of that type no matter which instance references it. In
addition, it can only use value of variables from the original type definition. These discipline
functions cannot be redefined in any type instance. The -t option turns on execution tracing for
this function. The -u option causes this function to be marked undefined. The FPATH variable
will be searched to find the function definition when the function is referenced. If no options
other than -f is specified, then the function definition will be displayed on standard output.
If +f is specified, then a line containing the function name followed by a shell comment contain-
ing the line number and path name of the file where this function was defined, if any, is dis-
played. The exit status can be used to determine whether the function is defined so that typeset-f.sh.math.name will return 0 when math function name is defined and non-zero otherwise.
-b The variable can hold any number of bytes of data. The data can be text or binary. The value is
represented by the base64 encoding of the data. If -Z is also specified, the size in bytes of
the data in the buffer will be determined by the size associated with the -Z. If the base64
string assigned results in more data, it will be truncated. Otherwise, it will be filled with
bytes whose value is zero. The printf format %B can be used to output the actual data in this
buffer instead of the base64 encoding of the data.
-h Used within type definitions to add information when generating information about the sub-vari-
able on the man page. It is ignored when used outside of a type definition. When used with -f
the information is associated with the corresponding discipline function.
-i Declares vname to be represented internally as integer. The right hand side of an assignment is
evaluated as an arithmetic expression when assigning to an integer. If n is non-zero, it defines
the output arithmetic base, otherwise the output base will be ten.
-l Used with -i, -E or -F, to indicate long integer, or long float. Otherwise, all upper-case char-
acters are converted to lower-case. The upper-case option, -u, is turned off. Equivalent to -Mtolower.-m moves or renames the variable. The value is the name of a variable whose value will be moved to
vname. The original variable will be unset. Cannot be used with any other options.
-n Declares vname to be a reference to the variable whose name is defined by the value of variable
vname. This is usually used to reference a variable inside a function whose name has been passed
as an argument. Cannot be used with any other options.
-p The name, attributes and values for the given vnames are written on standard output in a form
that can be used as shell input. If +p is specified, then the values are not displayed.
-r The given vnames are marked readonly and these names cannot be changed by subsequent assignment.
-t Tags the variables. Tags are user definable and have no special meaning to the shell.
-u When given along with -i, specifies unsigned integer. Otherwise, all lower-case characters are
converted to upper-case. The lower-case option, -l, is turned off. Equivalent to -Mtoupper.-x The given vnames are marked for automatic export to the environment of subsequently-executed com-
mands. Variables whose names contain a . cannot be exported.
The -i attribute cannot be specified along with -R, -L, -Z, or -f.
Using + rather than - causes these options to be turned off. If no vname arguments are given, a list of
vnames (and optionally the values) of the variables is printed. (Using + rather than - keeps the values
from being printed.) The -p option causes typeset followed by the option letters to be printed before
each name rather than the names of the options. If any option other than -p is given, only those vari-
ables which have all of the given options are printed. Otherwise, the vnames and attributes of all
variables that have attributes are printed.
ulimit [ -HSacdfmnpstv ] [ limit ]
Set or display a resource limit. The available resource limits are listed below. Many systems do not
support one or more of these limits. The limit for a specified resource is set when limit is specified.
The value of limit can be a number in the unit specified below with each resource, or the value unlim-ited. The -H and -S options specify whether the hard limit or the soft limit for the given resource is
set. A hard limit cannot be increased once it is set. A soft limit can be increased up to the value of
the hard limit. If neither the H nor S option is specified, the limit applies to both. The current
resource limit is printed when limit is omitted. In this case, the soft limit is printed unless H is
specified. When more than one resource is specified, then the limit name and unit is printed before the
value.
-a Lists all of the current resource limits.
-c The number of 512-byte blocks on the size of core dumps.
-d The number of K-bytes on the size of the data area.
-f The number of 512-byte blocks on files that can be written by the current process or by child
processes (files of any size may be read).
-m The number of K-bytes on the size of physical memory.
-n The number of file descriptors plus 1.
-p The number of 512-byte blocks for pipe buffering.
-s The number of K-bytes on the size of the stack area.
-t The number of CPU seconds to be used by each process.
-v The number of K-bytes for virtual memory.
If no option is given, -f is assumed.
umask [ -S ] [ mask ]
The user file-creation mask is set to mask (see umask(2)). mask can either be an octal number or a sym-
bolic value as described in chmod(1). If a symbolic value is given, the new umask value is the comple-
ment of the result of applying mask to the complement of the previous umask value. If mask is omitted,
the current value of the mask is printed. The -S option causes the mode to be printed as a symbolic
value. Otherwise, the mask is printed in octal.
+ unalias [ -a ] name ...
The aliases given by the list of names are removed from the alias list. The -a option causes all the
aliases to be unset.
+unset [ -fnv ] vname ...
The variables given by the list of vnames are unassigned, i.e., except for sub-variables within a type,
their values and attributes are erased. For sub-variables of a type, the values are reset to the
default value from the type definition. Readonly variables cannot be unset. If the -f option is set,
then the names refer to function names. If the -v option is set, then the names refer to variable
names. The -f option overrides -v. If -n is set and name is a name reference, then name will be unset
rather than the variable that it references. The default is equivalent to -v. Unsetting LINENO,
MAILCHECK, OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their special meaning even if they are
subsequently assigned to.
wait [ job ... ]
Wait for the specified job and report its termination status. If job is not given, then all currently
active child processes are waited for. The exit status from this command is that of the last process
waited for if job is specified; otherwise it is zero. See Jobs for a description of the format of job.
whence [ -afpv ] name ...
For each name, indicate how it would be interpreted if used as a command name.
The -v option produces a more verbose report. The -f option skips the search for functions. The -p
option does a path search for name even if name is an alias, a function, or a reserved word. The -p
option turns off the -v option. The -a option is similar to the -v option but causes all interpreta-
tions of the given name to be reported.
Invocation.
If the shell is invoked by exec(2), and the first character of argument zero ($0) is -, then the shell is
assumed to be a login shell and commands are read from /etc/profile and then from either .profile in the cur-
rent directory or $HOME/.profile, if either file exists. Next, for interactive shells, commands are read from
the file named by performing parameter expansion, command substitution, and arithmetic substitution on the
value of the environment variable ENV if the file exists. If the -s option is not present and arg and a file
by the name of arg exists, then it reads and executes this script. Otherwise, if the first arg does not con-
tain a /, a path search is performed on the first arg to determine the name of the script to execute. The
script arg must have execute permission and any setuid and setgid settings will be ignored. If the script is
not found on the path, arg is processed as if it named a built-in command or function. Commands are then read
as described below; the following options are interpreted by the shell when it is invoked:
-D Do not execute the script, but output the set of double quoted strings preceded by a $. These strings
are needed for localization of the script to different locales.
-E Reads the file named by the ENV variable or by $HOME/.kshrc if not defined after the profiles.
-c If the -c option is present, then commands are read from the first arg. Any remaining arguments
become positional parameters starting at 0.
-s If the -s option is present or if no arguments remain, then commands are read from the standard
input. Shell output, except for the output of the SpecialCommands listed above, is written to file
descriptor 2.
-i If the -i option is present or if the shell input and error output are attached to a terminal (as
told by tcgetattr(2)), then this shell is interactive. In this case TERM is ignored (so that kill0
does not kill an interactive shell) and INTR is caught and ignored (so that wait is ). In all cases,
QUIT is ignored by the shell.
-r If the -r option is present, the shell is a restricted shell.
-D A list of all double quoted strings that are preceded by a $ will be printed on standard output and
the shell will exit. This set of strings will be subject to language translation when the locale is
not C or POSIX. No commands will be executed.
-P If -P or -oprofile is present, the shell is a profile shell (see pfexec(1)).
-Rfilename
The -Rfilename option is used to generate a cross reference database that can be used by a separate
utility to find definitions and references for variables and commands. The filename argument speci-
fies the generated database. A script file must be provided on the command line as well.
The remaining options and arguments are described under the set command above. An optional - as the first
argument is ignored.
RkshOnly.Rksh is used to set up login names and execution environments whose capabilities are more controlled than those
of the standard shell. The actions of rksh are identical to those of ksh, except that the following are disal-
lowed:
Unsetting the restricted option.
changing directory (see cd(1)),
setting or unsetting the value or attributes of SHELL, ENV, FPATH, or PATH,
specifying path or command names containing /,
redirecting output (>, >|, <>, and >>).
adding or deleting built-in commands.
using command-p to invoke a command.
The restrictions above are enforced after .profile and the ENV files are interpreted.
When a command to be executed is found to be a shell procedure, rksh invokes ksh to execute it. Thus, it is
possible to provide to the end-user shell procedures that have access to the full power of the standard shell,
while imposing a limited menu of commands; this scheme assumes that the end-user does not have write and exe-
cute permissions in the same directory.
The net effect of these rules is that the writer of the .profile has complete control over user actions, by
performing guaranteed setup actions and leaving the user in an appropriate directory (probably not the login
directory).
The system administrator often sets up a directory of commands (e.g., /usr/rbin) that can be safely invoked by
rksh.
EXITSTATUS
Errors detected by the shell, such as syntax errors, cause the shell to return a non-zero exit status. If the
shell is being used non-interactively, then execution of the shell file is abandoned unless the error occurs
inside a subshell in which case the subshell is abandoned. Otherwise, the shell returns the exit status of the
last command executed (see also the exit command above). Run time errors detected by the shell are reported by
printing the command or function name and the error condition. If the line number that the error occurred on
is greater than one, then the line number is also printed in square brackets ([]) after the command or function
name.
FILES/etc/profile
The system wide initialization file, executed for login shells.
$HOME/.profile
The personal initialization file, executed for login shells after /etc/profile.
$HOME/..kshrc
Default personal initialization file, executed for interactive shells when ENV is not set.
/etc/suid_profile
Alternative initialization file, executed instead of the personal initialization file when the real and
effective user or group id do not match.
/dev/null
NULL device
SEEALSOcat(1), cd(1), chmod(1), cut(1), egrep(1), echo(1), emacs(1), env(1), fgrep(1), gmacs(1), grep(1), newgrp(1),
pfexec(1), stty(1), test(1), umask(1), vi(1), dup(2), exec(2), fork(2), getpwnam(3), ioctl(2), lseek(2),
paste(1), pathconf(2), pipe(2), sysconf(2), umask(2), ulimit(2), wait(2), wctrans(3), rand(3), a.out(5), pro-
file(5), environ(7).
Morris I. Bolsky and David G. Korn, TheNewKornShellCommandandProgrammingLanguage, Prentice Hall, 1995.
POSIX-Part2:ShellandUtilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2, IEEE, 1993.
CAVEATS
If a command is executed, and then a command with the same name is installed in a directory in the search path
before the directory where the original command was found, the shell will continue to exec the original com-
mand. Use the -t option of the alias command to correct this situation.
Some very old shell scripts contain a ^ as a synonym for the pipe character |.
Using the hist built-in command within a compound command will cause the whole command to disappear from the
history file.
The built-in command .file reads the whole file before any commands are executed. Therefore, alias and una-lias commands in the file will not apply to any commands defined in the file.
Traps are not processed while a job is waiting for a foreground process. Thus, a trap on CHLD won't be exe-
cuted until the foreground job terminates.
It is a good idea to leave a space after the comma operator in arithmetic expressions to prevent the comma from
being interpreted as the decimal point character in certain locales.
KSH(1)